This may seem random and does not come with a whole lot of 4E DM experience so take this for what its worth.

I am not sure if this is what you are looking for or not, but here goes....
Encounter Type or Feel and Difficulty
First you may want to figure out feel and difficulty you want.
Perhaps you want a light fun little skirmish or a knock-down, drag-out, knuckle-biting tactical slug fest. Both of those can be built similarly, but will have drastically different design considerations.
A light-hearted skirmish might have a fun little bit of terrain or an obvious trap that is there just for flavor or purely for the DM's amusement.
The later will most likely be a well thought out resource drainer, and the former quick and fun.
Monster Roles and Function
All of this section is predicated on having a good feel for what the monster roles are and how they affect an encounter. If you do not have a good feel for that you will want to take a close look a it. I think the next examples can kind of illustrate it.
Once you have the feel and difficulty decided you can take a look at the monsters and their roles. You may find ability synergies in there. Each creature now plays very differently.
An encounter with
4 artillery and
one brute will feel and play drastically different than one with
1 Controller,
2 Soldiers,
4 minions, and a
leader.
Perhaps you can have the Leader party level +3 and the 2 soldiers at level +1 and the minions at level. Not so easy and sweat worthy.
Perhaps the
4 artillery will be at level and the
brute will be an Elite Brute at level +1 or +2. Ouch!
Encounter Flava
Now, we have traps and terrain all of which can make things really interesting for your as DM and for the players as well.
You can select terrain that favors either one side of the encounter or the other, or perhaps one that hinders both if they are not careful.
Perhaps your creatures have a power that has bonus against cold vulnerable creatures. They you may want to add a trap or a terrain that bestows Cold Vulnerability to those caught in its wake.
Another facet of terrain fun are things like a cave riddled room or a room with ledges and ledges all around it, or a bunch or pits for people to fall or be pushed into. These will create a dynamic and potentially frustration encounter especially if one side or the other can take advantage of it.
You could just look through the laundry list of abilities from the creatures of the encounter and then just brainstorm a trap or terrain that could be used to take advantage of it. The DMG has some guidelines for creating or modifying them to suit your encounters needs, as well as examples for you to use.
Vice Versa
This could also be done the other way around as well.
If you have a terrain or trap that you want as the center piece of the encounter or will have a major influence on it you can start with that.
Perhaps your encounter take place in a cavern strewn lava flows and a small amount stalagmites. Start with that and then find some creatures that can push or can gain a bonus when in hot terrain, and then keep going...