Preps for a tornado that I took were

1. Build concrete shelter down in my basement
2. Stock it with alternate heat,cooking and lighting and frig.
3. Stock food, water ( I have a well ), porta potty, TP of course
4. Tools to dig out
5. Let someone know your going down there in case you can't dig
your way out.
6. Personal items as well as games and books
7. Bunk beds, with bedding
8. Weather Radio
9. Hand held Ham Radio
10.Extra batteries

Just a few basics, I have other supplies not listed, it's not just for tornado's

The only thing I haven't done yet is add a air filtration system to it. I also want to get my Ham License and a good base unit.

A good Weather Radio is top priority.