1. Get a glove, so you don't get bit by the rat, which is the most disgusting thing that can happen to anyone, ever.

2. Grab the rat by the tail and hit it against something hard. The floor works wonderfully.

3. Profit.

*disclaimer*

The rat will have a crappy time while you are doing this.

If you are with that (like I am), there you go. If you are not o.k. with this, there are other methods in which the rat may or may not have a slightly better day (conjecture imo, but I don't talk to rats so I can't argue one way or the other)....right up until the point it gets constricted and swallowed by the snake, which will occur about 30 seconds after whichever method you do choose.