If you practice a skill you haven't got, will you eventually get it?
Not directly, no. If your guild/subguild eventually gets it, you will branch it from practicing a skill you already have. If your guild or subguild does not get it, you will not be able to learn the skill. We have very occassionally granted requests to have skills added through special roleplay circumstances, but these are very very rare.
Related question: can someone teach you a skill that your guild is able to branch but that you haven't gotten yet?
They can teach you, but it won't branch until it's ready to branch.
Now I'm confused. What, beyond magick, is the purpose of the "teach" skill, then?
Um, if you are learning say "parry" from a teacher, and you have it on your skill list (but suck at it) he can help you get better?
Ah, heh. I was misled. Thanks.