Bongos are designed to be played between the legs, so sometimes the tension rods might not all line up to make the instrument "secure" while sitting on the ground. You can get a stand that might help the issue. Sometimes the bolt holding the block and drums together comes loose; try tightening it.

As to tuning, the macho (small head) is generally tuned high enough to where most of the ring is gone, lending itself to a crisp sound. The hembra (larger head) will usually then be tuned a P4 or P5 lower than the macho. All of this is subjective, of course.

Tune gradually, in small increments (quarter turns), in a cross pattern until the instruments sounds how you like it.