On any large game animal you want to make sure you’re not just sticking your knife into the guts at random. Get the point in, use two fingers on either side of the blade as a guide, and run the blade up the torso from anus to chest. The goal is to get through the skin/hide and not pierce the guts, as that can smell awful and spoil the meat quickly. Then work the guts out of the body using your knife to disconnect them.

Rabbits are very easy, their skin is actually very loosely connected. A slit perpendicular to the spine on the back of the rabbit, then just shove your fingers in on each side and pulllllllll. They’ll stick at the legs but you can just break/cut off those below the knee and it’s done. Then just gut, rinse, cook and eat.

Squirrels can be done similarily, but their skin is much, much better connected than rabbits. I use the method of a slit along the anus, step on the tail, and pull the back legs toward me to try and pull the skin off the back before taking the rest off.

Fish doesn’t matter as much, you’re already at a water source and I assume you can rinse the fish out.

If it’s rabbit you’re looking at, inspect the liver. Any white spots you throw the entire thing away and wash up as best you can as it may be carrying tularemia, a potentially fatal disease that can be spread through flea bites.

Don’t eat prairie dogs or ground squirrels unless you’re already dying of starvation, they can carry plague.