Hrqls: To surround territory is better: you can get more points with less stones.

In the beginning: claim a empty corner on the 3th or 4th line. Moves on the 1st and 2nd line are nearly always bad untill the endgame.

When attacking a stone you are one move behind, so that's a dangerous strategy.

And: opponents are allowed to have territory also, but not more than you have