How do you tell if a bunny is female or male but without looking at there private parts?

You don't. The only way to know if a rabbit is male or female is to examine the genitalia. Anything else is pure guesswork.

There are some behaviours and appearances that are more common in female rabbits than males, but they're not an exclusive rule. For example, just like how a human female might look "masculine" if she's tall, has a broad back, and wears her hair short, so a rabbit female could be mistaken for a male if her face is kind of squarish and she doesn't have much a dewlap.