The difference between ring games and tournaments really shouldn't be anything extreme as far as your play goes. A common mistake is to try and have a diff strategy for ring games and for tournys. While there are some differences between the two don't feel like you really need to revamp your game. Look to take adavantage of pots that are paying you good odds
to go ahead and take your draw, since you have the ability to rebuy now.
As for buy-ins i totally disagree with always trying to buy in for the max, another common mistake, many players feel intimidated by a big stack, or that they need to keep up with a large stack to play well, Im not saying that stack isn't important, but you shoud never be intimidated by the amount of chips. Find a buy in that you are comfortable with, 40 or 50xbb is a good start.