How to handle handicap as white?
There are a few good books about handicap go.

Handicap Go is a really good one, but it's out of print.

Get Strong at Handicap Go has a lot of examples of good play by both White and Black.

Kage's Secret Chronicles of Handicap Go discusses handicap games played between two professional players of nearly the same rank. It also includes reviews of games with professionals giving stones to amateurs.

In a high-handicap game, avoid strengthening Black's stones. If Black plays correctly you won't be able to avoid this, but then you need to lower the handicap.  You need to keep your groups light, and think about sacrificing often.  Many times you can convince Black to capture a few unimportant stones in gote.  As long as you keep from making Black too solid, you should be able to exploit shape problems later in the game, and in the endgame you should be able to pick up 20 points or so.  Also, never resign.  You never know when Black will give you a gift :)