I've read Tricia say that if you do TOO many of those offers in too short a time, your likelihood of getting credits go down. I don't know why, I guess it has to do with cookies, but I know I can rarely get too many in one week.
Are you doing surveys? That's 80 cents for each completed and credited survey. If you haven't tried them before, do the surveys SLOWLY, read a question and take a sip of coffee, think about it, answer it, take another sip, click "continue"...do the same. Even for "male vs female" or "how old are you" questions.

Before doing a survey, check their forums for the Daily Survey thread, to find out if the survey you're about to embark on is easy, ages long, etc. If I'd listened to them, I would have had an extra 45 minutes yesterday. Then again, it was nice to come back to that 80 cents this morning!
And when you do complete a survey, to make sure you won't be disappointed the next day, go through to TRY to get another survey. If the system lets you, the survey you just did didn't credit. If it tells you you exceeded the limit, you'll almost surely get credit.
Anyway, that might be more than you wanted to do, but then again, you'll get less email from random companies like you'll get after doing the offers!
