Well, I love DMing high magic games and love playing in them even more. The first thing I have found is that I used to be scared of high magic mainly because of balance. I was always concerned that the more magic I let in, the harder to balance the encounter. Much easier to let the party fight orcs and NPC fighters forever, lest I throw them something too tough and they die.
But then I realized my philosophy was all wrong. I now have no problem liberally giving out treasure and magic items, because I realized that if I'm liberal with the magic and the treasure, I can also be liberal with encounter difficulty. I have given the party enough resources that if they die in an encounter, then its because they played poorly, not because I didn't "balance" the encounter. Now granted, you can't throw a great wyrm at 5th level PCs but, if my 5th level PCs feel like going to the Troll marsh and they get their asses kicked, then that is their fault for not recognizing their own limitations.
I have found that what works for me is that I run a largely status quo world then I have my main adventure path. The main adventure is generally geared towards the level of the party in terms of difficulty. Everything else is not. I also don't worry about whether the party will have the resources to defeat a certain obstacle or creature. As long as the EL is close to the average party level, then its up to them to overcome it. In return, I'm pretty liberal with the treasure.
Another key to my success is that I don't let it bother me if the party completely bypasses something I had planned for them to encounter. In fact, I try to force them to come up with creative solutions by not even bothering to figure out how they can achieve something. That is up to them to figure out. For example, for a group of 5th level PCs, I might put a sheer 100' foot deep pit in the middle of my dungeon with the object of their quest somewhere below. How do they get down there? Well, thats the PCs problem. Its up to them to use their resources, spells, items, and class abilities to figure out a way down. If I know the party is off sufficient level to have access to Teleport, (even if there is no arcane caster in the party!), I'll put in a room with no physical entrance. How do they get in? Well, thats up to them. They should have sufficient resources even if they lack the obvious one such having someone who can cast Teleport.
I also don't pull punches with monsters. I often give my creatures max hit points, and if they need it, class levels too. If the party can wipe the floor with an Ogre, how about 4 Ogre fighters armed and armored with near max hit points? Now they have a fight on their hands.
One thing, I'll recommend is you should also know the PHB and the DMG like the back of your hand. I strongly suggest reading both books cover to cover. Also if you intend to use a monster, be sure to review all of their special attacks and abilities in advance so you feel comfortable unleashing them on the party. Also play your opponents intelligently (or at least realistically if they aren't smart). For example if Drow are going to ambush the party, they will do it right. They will observe secretly, see if they can identify spell casters, and then when the ambush is sprung they attack by dropping Silence, globes of Darkness and such to sow maximum confusion on the party. I don't pull any punches.
But in exchange, my PCs get to keep all the cool magical gear they would get if they kill the drow. I'm liberal about letting them sell such loot and even having custom magical items built for them. Such things cost money or favors they owe to the mages who make it, but that in turn leads to further adventures and more fun. For my everything-goes-D&D-to-the-max play style, I have found the Realms works best for me. And high level NPCs are not a problem for me for the simple reason is that for every save-the-world quest the PCs might be on, well Elminster is juggling two or three of his own and doesn't have time to deal with PCs. Or if PC's think all that magical gear makes them gods, its pretty easy to have some high level lord get offended and send some high level uber goons to take them down a peg.
Anyway, the bottom line is have fun.