As someone whose been DM'ing homegames since second edition was released and run hundreds of RPGA events, I can offer a few decent tips for speeding up homeplay. I'm sure many of the experienced hands around here do the same, but i'll re-iterate them for new DM's. Here's a few things we do to keep the ball rolling.
1)
End most campaigns around 15th level (though i perfer 12 myself) ESPECIALLY if you have lots of new players. 3.5 as we all know begins to fall apart at levels higher than 14. Combats start taking forever, no one remembers what high level spells do, your meelers have to roll a zillion dice every turn, etc, etc. Of course if your a fan of epic play, then by all means keep going
2) make your lives easier and more fun, take away critial conformation rolls.
3)
Use a Dm screen and learn to LIE to your players. Your all there for fun, sometimes you need to fudge the rolls for or against your players to keep the story (and the fun) going.
4)
Create DC's on the Fly. THis is something i learned waaay back in West End Games old star wars RPG. Who cares what the DC is for tying a sheepshank knot? And why spend 2-5 minutes looking it up? When faced with things like skill ckecks, as the DM just pick a reasonable sounding DC. Its fast, easy and convenient. Your the DM, your players trust you and your word overrrides whatevers printed. So save you and your table precious minutes and make more "on the Fly" rulings.
5)
Skip miniatures for simple battles: Seriously, you really don't need to draw out a 20 by 20 room with just 2 orcs and a table in it. Have thier players describe thier actions and run with it. Sure, with things like cleave and whirlwind and AoE, you'll have to decide whether the monsters are in range, but thats your job as a dm, So have fun with it and improvise. (seriously folks, not having to sit there for 5 minutes while Joe fighter figures out which 6 squares he's going to walk through to get to the big baddie is a MAJOR time saver, so try a few enounters "old school" style and skip the miniatures.
6)
Ignore Hit points, know when to kill your monsters": Again this is why you use a DM screen. Who cares how many hit points are written on the paper in front of you. If the time is right, let it die. Your two main times to do this are when
(A) the combat is running on forever and getting boring or
(B) when someone does something really heroic and you want to create a dramatic bit of flair.
Example: The Uber tripping reach monster with a spiked chain you created is great, but when combat drags on for 15 rounds sometimes its time for the thing to die, regardless of its hit points.
-or-
The hero dashes across the room, sucks up 4 Attacks of oppurtunity, dives across the altar (making his jump check), and stabs the bad guy in the chest right before the knife sinks into the hostage is a great time to kill your villian, no matter his hit points.
7)
Encourage your players to USE thier character sheets: Ask them to write down a few notes on thier favorite spell/item/feat/etc, so you dont have to look it up every few rounds when they use it. This falls into the above poster's comments about being prepared. Along the same line require your players to bring any appropriate builder books to the table, or they cant use thier feat/spell/item/skill/class/etc.
and lastly...
Order the pizza (or whatever) well before you take a break for food.

Nothing's worse than taking a 30 minure break, then ordering the pizza, then waiting for it to show up, etc, etc. Byt he time it arrives, you eat and get started again youve burned 60-90 minutes
Well thats about it for now. I stayed away from game mechanic changes, and focused on ways to really shave time off your encounters, and give the players more bang for thier buck for each hour at the gaming table. Hope its helpful
Duane
AKA Kassegore