Find a program to judge signal strength, then run around the area you want to use your laptop in and see what happens.
High is an alright idea, but too high is bad too; floors/cielings in the way degrade quality. Vertical antanas are a good idea, but only if you're going to be mostly on the same floor. Basicly, the broader view your card has of the antanna, the better. So if you're house is 5 floors tall and 6foot wide by 6 foot deep (ok, that's a little extreme, but have you ever been to apartments in the netherlands?) you may be better with either a horizontaly mounted antanna or multiple access points.
All you can do is trial and error.
Forgive the crappy spelling,
Pkcp