Well Derulbaskul has pretty much covered everything and given an excellent example of how to transform a PC to a monster.
For what its worth here is my general advice on the subject.
1. PCs and monsters use different creation systems.
2. PC and Monster powers are different.
The above two simple statements being true gives you the key to turning a PC from a character sheet into a monster stat block. Very simply put while there are many strict rules to follow when creating a PC there are very few rules to follow when creating a monster.
In other words you look at the character sheet for inspiration, but inspiration only. What you are looking for are the key elements that define the PC, for this try not to focus too much on specific powers or even their mechanics, try to focus on who they are and what they do.
Figuring that out should give you a good idea of what role the creature will have, this will give you the basic mechanics for the monster. The stats, HPs, Defences, Attack values and an idea of the damage range.
Once you have reached this stage the real fun begins. Now you need to give the monster enough powers to achieve your ideal solution while not making the monster too unwieldy to run. The balance here depends on the importance of the monster (basic, elite, solo), and the number of powers you need to represent its design role.
Obviously you should bear in mind the survivability of the creature, or in other words try not to give it so many powers that it will not have chance to use them all before it is dead. Remember that PCs are built with choice and survivability for over 30 levels in mind while a monster is usually designed for one encounter and is expected to die.
As this is basic general advice I am going to stop there.
Example (using the first PC stat block you gave):
Jared Silverhawk – Level 6 tempest fighter.
Step 1: Who/what is he?
From looking at the build this is a mobile fighter who uses 2 shortswords. He is happiest when he is moving about and attacking multiple targets.
Ok this tells me he is a skirmisher and for the purposes of this exercise I am going to say he is a named villain and make him an elite.
Step 2: Stats
Baseline for a level 6 elite skirmisher is
HPs 144
AC 20; Fortitude/Reflex/Will 18
Attack bonus +11 vs. AC; +9 vs. NADs
MM3 damage expectations: 2d6+7 (max 19) / 1d8+6 (max 14)
Step 3: Powers
Basic attack, everybody needs a basic melee attack.
Sword Jab (standard; at will)Attack +11 vs. AC; 2d6+7 damage
Elites above level 5 need an attack that can target 2 enemies, our monsters inspiration comes from moving and attacking multiple enemies so that fits nicely.
Double Sword Shuffle (standard; at will)Jared makes a Sword Jab attack against a primary and secondary target;
Jared may shift a total of 3 squares at any point before, between or after
these attacks
Now we have designed these two powers we have fulfilled our basic requirements, everything we add from this point is down to theme and flair. This is when you start to think about recharge and encounter powers, and traits and triggered actions.
This is also where we take another look at the monsters role. A skirmisher usually has good movement related powers and sometimes deals more damage under a certain circumstance (usually with combat advantage). As this is a level 6 elite I don’t really think it needs a bump in damage, but I do want to concentrate on movement.
One thing that immediately strikes me is that a fighters mark/challenge is going to stop any shifting away this monster can do, so I should design something with that in mind. At this point I also remind myself not to be too vicious as this is only a level 6 creature.
How about:
Push and Strike (standard; recharge 
)Primary target; attack +9 vs. Fortitude; 1d8+7 damage; on hit target is
pushed 1 square and knocked prone; hit or miss Jared may shift 2 squares
and make a Sword Jab attack against a secondary target
This attack is by no means optimal (it is less damage than his at will) but contains enough utility that it will be a good option in a tight situation. I made it a recharge 4 because I want it regularly available, but not necessarily every turn.
Wanting to add another layer of depth to the mobile nature of Jared and take inspiration from footwork lure I think about an interrupt action that might provide a few interesting tactical opportunities.
Draw Them In (immediate interrupt; recharge
) triggered actionWhen Jared is targeted by a melee attack by an adjacent enemy he may
shift 2 squares as an immediate interrupt, the target may choose to follow
Jared up and continue the attack or stay where they are and lose the
action
Well the list of powers is growing and we still need at least one encounter power looking at the inspiration list I see Funnelling Flurry and Tempest Dance. I also see Hounding Longarm and I don’t know what its on the list for as it requires a reach weapon which Jared doesn’t have, its effect is also quite fiddly.
Hounding Longarm does give me the inspiration for a power though.
Hounding Flurry (standard, encounter)4 attacks against the same target; attack +11 vs. AC; 1d6+7 damage; on
hit target is pushed 1 square and Jared follows up; after resolving all
attacks if 2 attacks hit the target is knocked prone, if 3 attacks hit the
target is knocked prone and slowed (save ends), if all 4 attacks the target
is knocked prone and dazed (save ends)
When I review the power I wonder if it could be too powerful. The max damage is 52, the max damage from 2 standard attacks is 38 but this is being shared by 2 separate targets.
I ponder it for a few minutes weighing up the pros and cons, it is 4 attacks rather than 1 so it is most likely that some but not all the attacks will hit, knocked prone and dazed is also a slightly cruel combination of effects. The MM3 rules for the damage from a limited attack is standard attack plus up to 50%, in this case that would be in the region of 28/29 damage, add in a second standard attack as its an elite and that increases it by 19 damage which is a total of 48 damage. That’s almost certainly too much damage especially when you consider that the monster has an action point available to it.
I really like the concept of power though so I am determined to get it into a usable state. In the end I plumb for reducing its accuracy and damage and toning the effects down. I also make a mental note to give some thought to the creatures optimal action point use.
Hounding Flurry (standard, encounter)4 attacks against the same target; attack +10 vs. AC; 1d6+5 damage; on
hit target is pushed 1 square and Jared follows up; after resolving all
attacks if 2 attacks hit the target takes a -1 penalty to attack rolls (save
ends), if 3 attacks hit the target instead takes a -2 penalty to attacks
rolls (save ends), if all 4 attacks the target is instead dazed (save ends)
It’s a big attack, he’s only got one chance to use it and my gut tells me it will be OK.
At this point I take a look at my powers list and think they are OK, I haven’t included anything for his items but as this is a level 6 creature I think I will leave them alone for the sake of simplicity.
He does need a little something extra though, so I turn my attention to his action point. Action Surge, Heroic Recovery and Boundless Endurance all strike me thematically about resolve under pressure. This fits with a defensive style bonus when he spends his action point, tying a defensive or healing bonus to his action point will also stop its use for going nova early in the fight. This could be a good thing.
Determined Action – trait, healing
When Jared spends his action point he also regains 30 HPs and gains a +2
bonus to all his defences until the end of his next turn
This is a nice little recovery as a pay off for holding back with the action point and will make him more resilient for a turn which is in keeping with his fighter background.
So lets have a look at our list of abilities:
Determined Action – trait, healing
Sword Jab (standard; at will) Double Sword Shuffle (standard; at will) Push and Strike (standard; recharge ) Hounding Flurry (standard, encounter)Draw Them In (immediate interrupt; recharge
) triggered actionLooking at the list it is still missing something so I go back to the items and like the look of cape of the Monteback so I add that in. Now as an example of monsters following different rules to PCs I decide to play with the cloak a little, it will still function as it does in the book if the PCs take it as loot but it will be slightly different for Jared.
Cape of Monteback (move, encounter) teleport
Jared teleports 5 squares and gains combat advantage against any enemy
he ends this move adjacent to until the end of his current turn
Step 4: Putting it all together
Now lets see what we’ve got.
Jared Silverhawk Level 6 Elite Skirmisher
Medium Natural Humanoid XP 500
Initiative +8 Senses Perception +4
HP 140; Bloodied 70
AC 20; Fortitude 19, Reflex 18, Will 17
Saving Throws +2
Speed 6
Action Points 1
Determined Action♦ trait, healing
When Jared spends his action point he also regains 30 HPs and gains a +2
bonus to all his defences until the end of his next turn
Sword Jab (Standard; at-will) Attack +11 vs. AC; 2d6+7 damage
m Double Sword Shuffle (Standard; at-will)
Jared makes a Sword Jab attack against a primary and secondary target;
Jared may shift a total of 3 squares at any point before, between or after
these attacks
Push and Strike (Standard; recharge ) Primary target; attack +9 vs. Fortitude; 1d8+7 damage; on hit target is
pushed 1 square and knocked prone; hit or miss Jared may shift 2 squares
and make a Sword Jab attack against a secondary target
Hounding Flurry (Standard; encounter) 4 attacks against the same target; attack +10 vs. AC; 1d6+5 damage; on
hit target is pushed 1 square and Jared follows up; after resolving all
attacks if 2 attacks hit the target takes a -1 penalty to attack rolls (save
ends), if 3 attacks hit the target instead takes a -2 penalty to attacks
rolls (save ends), if all 4 attacks the target is instead dazed (save ends)
Cape of Monteback (Move; encounter) ♦ teleportation
Jared teleports 5 squares and gains combat advantage against any enemy
he ends this move adjacent to until the end of his current turn
Draw Them In (Immediate Interrupt; recharge
) ♦ triggered action When Jared is targeted by a melee attack by an adjacent enemy he may
shift 2 squares as an immediate interrupt, the target may choose to follow
Jared up and continue the attack or stay where they are and lose the
action
Alignment Unaligned Languages common
Skills Athletics +12, Endurance +10, Streetwise +7
Str 19 (+7) Dex 16 (+6) Wis 12 (+4)
Con 14 (+5) Int 10 (+3) Cha 8 (+2)
Equipment 2x shortsword, chainmail, cape of monteback
In this stage I make any final adjustments, paying special attention to HPs and Defences. In this case his Fortitude is 1 higher and his Will is 1 lower, roughly in line with his stats. I have a think about the effect of the extra 30 HPs Jared will get from Determined action and think that is will be fine.
My final assessment is that he is not terribly exciting, but is certainly a competent and reasonable threat.
Job done, onto the next one.
Conclusion
Well I am not sure if this post will be useful to you or not as it is all pretty much common sense. If it has come across as patronising I apologise.
Sword Storm (weapon) * Recharge 
