The easiest decision in Poker is about opening the pot. Nobody has shown aggression yet, the pot size is as small as it can be, so no costly error can be made.
On the other hand, you better get this part right! There are several reasons why opening the pot correctly is so important:
1) This situation happens all the time. In a big portion of your hands you will face this decision. Even if you only make small errors, they'll add up quickly.