Definitely learn to spell. Exhausting as fingerspelling is, as long as you know it, even if you don't know the sign, you can still get the message across and communiate.
The best way to learn it is to practice signing with someone. I guarantee you'll learn twice as fast this way. Try to hunt down local gatherings or events if you can.
Learn emergency signals: signs you'll need if you're in a hurry for something. Bathroom, water, etc.
Figure out an acronym for the different asl sentence structures. It'll make it easier to remember how the words are set up in an asl structure when conversing.
Don't freak out if you fall out of asl and contact signing. This happens a lot to people. XD
Best of luck!