One of the thing’s my group’s Stargate SG-4 GM, Don, does that I really like is handwave XP. Instead of awarding XP, he just tells us when we level up.
He has a keen sense for pacing, and we usually go up a level every couple of adventures (each adventure being one session). This pace is satisfying for us, and fits well with the tone of the game.
This approach is formalized in Green Ronin’s True 20 system (and I mentioned quite liking in my True 20 review), and it saves a lot of bookkeeping for everyone. It won’t work for every RPG or every group, but when it does work it’s a great approach.
Edit: One essential ingredient, at least for me, is that Don also awards Action Points (which, in d20 Modern, let you break the rules a bit) during sessions. This really makes the XP-by-fiat approach hum — see the comments below for details.