For many of the videos repeat watches are unlikely to count (sometimes they do but mostly not.) That is, the video we are 'randomly' sent, if sent to us again will not count ( I bet the services charge companies a 'unique viewer' option, and doesn't care if we repeat watch for nothing.)

Also, a few of the video servers want you to interact a bit. Either there is a bottom of the player button to acknowledge your done (sometimes it ready before the videos done!) Or they want you to click on the finished video to visit the site before they will credit you (Car commercials do this a lot. And they can be stingy if you don't click through that first time).

And surveys that start fishing for info, well.

Most of those don't like my demographic. Or are really poorly done (Do you barbeque? Yeah on gas-grill. Okay, here's some charcoal questions!)

Videos are your safest bet. Just very slow. And still be careful.