I agree that bluffing is an art form and there should be some thought process into the bluff just as there is thought to every other part of the game. Start with your opponents image, what do you have him on, does he call a lot, is he a bluffer himself (people who bluff a lot also call a lot because they are convinced that everyone else is also always bluffing). Move on to your own table image, have you shown any bluffs, have you shown many hands, are you winning a lot at showdown. Next is the situation. Playing a hand is like telling a story, does your story make sense. Did you check call, check raise and lead out, this is a strong move that is successful with big winning hands, so when you use it as a bluff then it looks like you have something hard to beat. But if you went check, check on the flop and turn and then lead out with a big bet when a disconnected 3 hits the river, the other player is probably going to be suspicious.
You also have to account for position, stack sizes, how deep in a tournament you are, how long you have been sitting with the same players, how close a break or the money bubble is, ect.
Ring games are similar, you have to account for table images, your image, what you've been showing at showdown, what others have been showing at showdown, when you can move a guy off of top pair with a well placed value bluff and when your just pissing your money away.
There are players that I will never bluff, there are players that I bluff often, but this is only after having solid reads on them. There are also situations that it make sense to bluff and there are situations in which everyone knows that your just bluffing. So, you have to take into account a lot of factors before you decide to bluff a hand, but to be successful at poker you HAVE to be able to bluff and semi-bluff. You cannot only play made hands and be successful.