This is old, but it has also been stickied, so I wanted to add my two cents for whoever may be looking at this later on.
EDH is highly dependent on the group you play with. If you are playing 1v1 games, expect fast games with a lower mana curve. If you are playing multiplayer (which I think is where the format shines), expect longer games with a higher mana curve. As I only play multiplayer, the rest of this is directed at that subsection of EDH.
You will need removal to handle the amazing cards that come out. Board wipes can be useful, particularly if you can work them into a one-way wipe.
Exiling is better than destroy effects, as there are many indestructible permanents out there that work fabulously in EDH.
Split second cards are better in EDH than usual. You never know how the politics of a multiplayer game will go, and invariably somebody has an instant or an ability that messes with your chances to do something.
Cards that take care of artifacts and enchantments should probably be in every EDH deck you make. There are many of these out there that drastically change the board state, and if you can't remove them, you get hosed- often in amusingly unpredictable ways, but still hosed.
As with all formats, adapt your strategies to the group you play with. Mine has a lot of board wipes, so running a creature deck isn't a great move unless those creatures can survive or do damage before getting wiped out. Your group may or may not run a lot of board wipes, or counter spells, or whatever else may ruin your day.