I really like sweeps that have separate entry points for the IW and GP/sweepstakes. Many times I'll like the lower tier prizes, but the GP will be a trip, so I *usually* pass them by if it's combined.
2nd best - the IW's that give ONE GP/sweepstakes entry throughout, so if you win an IW you can stop playing. If it's a 1ppp IW I stop entering if I win anyway, but I know others keep playing for that entry, and if they reaward the IW's, no biggie, but if they don't reaward ...
One time registration, with easy login re-entry. Especially for IW & daily. Even though I have roboform, sponsors sometimes change their forms/add survey questions mid sweeps.
I find 1x sweeps to be very time consuming, so I rarely enter them, whereas while daily/IW sweeps require time upfront, further entry is a snap.
Facebook is the exception for the 1x's - since I can't "unsee" them, while I'm looking for the good daily entry with daily/weekly/etc. prizes, I'll enter some of them.
I actually like FLASH forms at times - if I'm into only a few of the prizes, a FLASH form makes it easy to decide to NOT enter. Conversely, if I really like all/most of the prizes, I figure my chances might be a tad better since lots of sweepers dislike FLASH and will enter less often, if at all.
I usually *have* to enter all the sweeps I have saved when I enter, but, if I'm in a time crunch, the IW's and daily with daily/weekly/etc. prizes are the ones I'm most consistent on.