The real point is your question is way to vague.

You're asking how to call an all-in with no reads. Is this pre, on the flop, on the river? How did we get to the point that villain pushes? Did a draw hit, overcard, blank?

In general at microstakes accept the bet at face value (i.e. it is what it represents). The villains who bluff all-in a lot are maniacal and should be easy to spot. In general you should be putting the chips in, not calling.

Post hands, you'll get better advice that way.