Videos, for me. I do the carousel videos every other shot or so, then hopefully there are 5-view vids below that. Sometimes, those are not there for 2 weeks straight. Other times, they let you wear it out. Last week, I watched (well, actually I was playing WGT in another window) the same video over 20 times in a row. Five views each, 75 credits, TYVM.
I also do surveys, but not every day. I will "clear them out" every couple of days; most of them it takes 30 seconds of clicking and you are booted and given 5 credits.
If you really have no time for all that crapola, take a $10 bill to Subway, but a gift card, and go home and buy 1000 credits with it. I did that during a dry spell, when they weren't letting me get credits much, in order to buy the irons I wanted as soon as I qualified, rather than wait 6-8 weeks to earn the credits.