If this is your first time making hamantaschen, I have two pieces of advice:

1) chocolate chips are an awesome filling :)
2) be careful not to overfill! It's really easy to overfill, and when that happens, they unfold while they're baking, and the filling spills out and it's horrible and messy. I've made them a bunch of times and I still have a hard time getting it right. So use less filling than you think they need :)