I generally bet 2% of bankroll per game. I only vary from this becasue of perceived extra value in about 1 pick from 20, these have produced a higher edge than my standard edge over the long term.
Where I do vary quite a bit is the number of picks I make. In bad runs I "defend" - have only 2 or 3 bets open at any one time, these will be those where I think I can see the whites of the eyes.
In good runs I can have 15 or more open bets at once, it always amazes me just how long good luck can run for you in good patches. Some of the picks I take on in good runs I would leave alone - with regreats - in my bad runs.
Bad runs don't last so long when you adopt this approach to getting out of them.