Let me just start by saying I'm horrible at math... but I'd like to get better at quickly adding numbers in my head.

I'm not sure if this is the right place to ask, but I was wondering if any of you guys have suggestions or strategies on how to quickly add numbers <100 in your head.

If you know of any books that will help me out with this simple task, just let me know, but I would like to learn how you guys go about doing it, thanks!