If we are talking about a 9 players game and remains 4+ players after my bet, I try to bet a micro raise in a range of 1-3 BB.
If remains less than 4 players, I try to put a bigger raise.
But you will only do this if you think that your opponent will not fold your bet, because you want him playing the game as long as possible to steal more of his stack (if the game is not opening a possibility to a bad beat, of course).
You need, indeed, to watch your opponent plays in the table and try to figure out if he is folding, calling or 3-betting (4-betting, etc.) the raises on the pre-flop.
My careful strategy is based in: "Try not to scare the villain".