Anybody has any experience, links or suggestions on how to implement that sort of testing? I'm interested in things like how to put it in place, with which use

Anybody has any experience, links or suggestions on how to implement that sort of testing? I'm interested in things like how to put it in place, with which users, over what period of time, tools to analyze the results, etc. The concept is extremely simple: let's compare how people react to different design/layout/copywriting and pick the best one. In practice, it seems that there is quite a lot to put in place to track things properly. Is Google Analytics enough for this?