I bet 1-2% of bankroll for the most part. I occassionally go nuts and put a larger play out there that I feel real good about or cut back if its something I know is a stupid play.
I adjust the amount as bankroll goes up or down but try to sustain the 1-2% amount. If the bankroll changes a lot, then I redeposit or withdraw $$ to get back to a target.
I'm not in this to make a living and realize it is a marathon not a sprint to be successful.