Firstly, I ask the question: what genre is the game? It has to be of the genre I'm inclined to at that particular period of time, as my interest changes from time to time. However, it has generally revolved mostly within sport games.
Secondly, I check out or seek the reviews which the game has got. I don't go for anything less than a 4.O on a scale of 5. Reviews makes me rest assured of a nice playing time if I purchase the game in question.
Lastly, for hardware, I check out its specs, quality, durability, etc. For instance, I wouldn't go for something which I perceive, if purchased, wouldn't last up to a month before getting thrown in the thrash can.