First thing to decide is if you're staying at South Lake or Tahoe City (north). South Lake is "resort" town, with Casinos, all night dance clubs, lots of restaurants, etc. Plus, the gondola to Heavenly will pick you up right on the sidewalk. Busy, crowded.
Heavenly is great for a photo op. It is huge, you'll ride in two states at once (start in California, stop in Nevada for a beer, head back up for some tree runs through both). But it's wicked crowded and very touristy, and a very spread-out layout. I consider it a must-see for your first trip to Tahoe, but you might never go back after that.
Kirkwood, though, is the tits. It's serious shit. Everything from the drive through the Carson Pass to the trip up to Sentinel Bowl or (I dare you) The Wall, will test your abilities and give you memories that will last forever. Don't miss the back side, The Wave. And don't dismiss the "beginner" areas. Some of the most fun greens and blues you'll ever do, with deep ravines and beautiful glades to play in. If the weather is bad, better make sure you have good tires on your 4x4, and pack a bag. If it snows really hard (which it does a lot at Kirkwood, more so than anyplace else at Tahoe) you might wind up being forced to spend the night. No alternate ways out.
Consider the North Shore/Tahoe City for a more relaxed "California" vibe. For the best in ski-in/ski-out (and to impress the parents) go to Northstar. Not the best riding, but it is a serious tourist resort, complete with a Ritz-Carlton Hotel with chrome gondola, where the lifties place a blanket over you for the ride up. Seriously. Your parents can shop at the mall (yup, this place is like a mall with a ski slope next to it) while you hit "The Stash," Burton's all-wood terrain park. The regular trails aren't awesome, but they're fun. It's much more like a Vermont mountain than anything else at Tahoe; mostly trails cut through the woods, instead of the wide open bowl and chutes of places like Squaw or Alpine or Sugarbowl.
There are a few major resorts on the North Shore all within minutes of each other, including Squaw Valley, which still has the whole Olympic village thing going on. It's got a beautiful mountain-top restaurant/skating rink/swimming pool, and a very nice restaurant. Plus, some of the most varied terrain you'll find, with lots of steeps, bowls, chutes, off piste, you name it. And even views of the lake. Alpine is on the other side of Squaw, and your lift ticket is good for both mountains (although Squaw is so big, you could ride for three days and not be done with it). Alpine is just for serious riding and skiing, because the lodge isn't much to hang out in. But the terrain is awesome.
Probably the prettiest place on the lake is Homewood. It's much smaller than the other mountains, but it is literally right on the lake. Several trails will freak you out, as you feel like you're going to ride right into Lake Tahoe. Bring an extra SD card for your camera...you'll take a TON of photos. And it's cheap. Plus, the parking is easy...it's like pulling off the road into 7-11. Get there early, and you literally park 50 feet from the lift. There are only a couple of greens on the whole mountain, and great glades. Plus "Quail Face" and the 55 Chutes. Steep-ass, wide open bowl. Lots of fun, but takes a hike to get in and out.
If you want another fun drive (which you might do anyway on your way in from Reno), hit up Mt. Rose. Crazy steep chutes, some nice long blacks down the front, beautiful winding blues and greens through the trees, great views of Reno, the valley and the desert, and wicked cheap during the week.
Don't pass up Sugarbowl, either (a drive through the infamous Donner Pass). Chutes, glades, bowls, lots of fun.
Diamond Peak is on the Northeast side. Unless you find a $10 ticket somewhere, skip it. It is beautiful, but gets boring fast. Advertised as the kid's mountain.
Never been to Sierra, but I hear it's fun.
So there you go! Have fun (BTW, check out Shell stations near Reno...they usually offer 2 for 1 Northstar tix with a fill up). Have fun!