I'll always check the achievement list on games I play, and do the ones I think look interesting or fun. I tend to ignore any achievements that require excessive grinding however, like the 'collect 100 extremely well hidden very small useless items' so many games are fond of.
My favourite types of achievements are the inventive one, for example,
Just Cause 2 had a bunch of achievements that required you to kill enemies by throwing them off heights, running them over, or attaching a tank to a helicopter and using it like a wrecking ball.
I've gotten 100% in a few games, and I get a bit of satisfaction from doing it, but I won't go out of my way for 1000GS.