Hi kflanagan
The best piece of advice I can give you is to RTFR (that means Read The Freakin Rules). And read them carefully. Her's why...
Sweeps #1 - Win a New Camaro! this contest is 1 entry per person, per email, per household.
This means they are going to look to see if you submitted more than once using different emails or names and if the household address is the same. If any of those show more than one entry, you're disqualified and I get to win the car

But, if you want to enter under Uncle Bob's profile and he has a different email address AND household address, you're safe. Just keep in mind that most affidavits will also require you to provide a scanned ID to prove who you are (in this case, Uncle Bob).
Sweeps #2 - Here's a new daily ( http://www.winmikes.com/stevearpin/ ) - the rules state "Restrictions : 21+ IL, IN, IA, OH , TX | Limit : 1 Per Person / Email Per Day" ... so, first make sure you live in one of those states (and are 21+), or the person your entering for lives in one. Next, you can enter 1-time per day. So can Uncle Bob, your 3 kittens, 2 dogs, 17 fish and your aardvark, as long as they have different emails. Note that they need to have separate, VERIFIABLE email accounts. So rush on out, sign the aardvark up for hotmail, a kitten or 2 on gmail, some fish on yahoo and so on. There are tons of "free email" services out there and as long as the accounts are verifiable (and you can provide a scanned ID for the winning account holder), you can really cash in!
In a movie (Real Genius) there was this geek who had printed out like a million mail-in entries for a big sweeps. When asked if he felt that doing so was kind of "taking the fun out of it" he replied "Well, THEY made the rules (unlimited entry) and lately I've realized that I need certain materialistic things too..."
Sponsors have since gotten much wiser about the rules because they've come to realize that seasoned sweepers will certainly read them and play by them.
There are other types of sweepstakes and associated rules (some may be rather odd) but I hope the above helps explain it a bit for you. Sign up for Sweepstakes University on my Sweeping Friends website and watch a video of me explaining all about "RTFR" and not only how NOT to get DQ'd, but rather how to improve your chances of winning by playing by THEIR rules!
-Fish