Car A/C recharge, DIY?

[rgG]

I used to recharge the AC on my old Ford van, as it had a small leak that apparently they could not fix.
My dad showed me how, and after that it was very easy.
I need to figure out how to do it on my Miata, as it has the same problem, even after having the compressor replaced a few years ago.
Right now, I have the top down, instead of the AC on.