Best way to go about learning asm (I MEAN FULL COMPREHENSION)

What can I do to learn asm besides school? And I mean really learn it so that I can debug, do some reversing, etc?

And what's best to learn from and use? TASM, NASM, or MASM?

masm is the common stuff, but asm is asm it doesn't really differ much. it's only about asm optimization like if you are planning to make program ports etc.

the reversing with lena tuts should be the first thing to go with!