Use SA correctly. You need to click the links and fill out the entry forms to enter. SweepsCheck is a great tool, but checking it off does not enter you in the sweepstakes.
If you use an autofill program - double check your info is correct. And ALWAYS double check the entry form before you submit
Entering too often - always check the category/rules to ensure you don't DQ yourself.
Not entering often enough - if you sweep 1 - 3 times a week, you will have less chances.
Confining yourself to only IW sweeps/1x entries/dailys/etc - mix it up & try to enter any and all categories.
Entering for those you aren't eligible - like: if you make up a company name to enter, you enter a sweeps that is only for residents of Canada, etc. Always check the restrictions.
Entering too few sweeps - I'm not suggesting you enter for prizes you don't want/can't regift, but don't restrict yourself either!
Entering sweeps with very few prizes - even though that seems to be the trend of late, try to enter sweeps with LOTS of prizes.