anybody know if the brake calipers on a 96 suzuki x90 are twist back or squeeze back?

Can't say I've run into any of those, considering they only sold about 8K of them over the course of 3 years, and probably mostly on the coasts at that. But basically, there are 2 predominate setups for rear disc brakes.

One is where the parking/emergency brake function is built into the caliper. These are the ones that need to be turned back in. Look for a piston with a flush face (not hollow), and a couple little indentations where the inner pad sits. Also, a cable attached to the back of the caliper.

On these, use the tips of a needle-nosed pliers pushed into the indentations of the piston to twist the piston back in. You really don't have to push the piston in, just push enough to keep the tips of the pliers from slipping out. The screw behind the piston will pull it in as you rotate it (usually clockwise).

When you put the pads in, make sure the indentations are lined up and down (relative to the caliper body), so that the little knobs on the pads line up with them. After you get it all put together, engage and release the parking brake a few times to adjust the pads.

The other main type is what's called "drum in hat". This is where the center of the rotor has a bigger hub area in it, where they install a small set of brake shoes, like with drum brakes. These act as the parking/emergency brake. The calipers used with this setup push back in like normal front calipers.

Besides the bigger rotor hub, these can be recognized by the backing plate to hold the shoes in place, and the fact that the cable for the parking/emergency brake attaches there instead of the caliper.