You can eat as much of them as you can handle that adds up to the amount of carbs you need in a day (less the post-workout carbs).
They are one of, if not the, best sources for carbs you can eat.
As far as preparing them, I just put one in the microave with a paper towel wrapped around it, for about 5 minutes.
It's not bad, but I'm sure baking it tastes better.
I've also added that zero calorie butter spray stuff for taste when I started to get sick of eating the same thing over and over.