Just keep the flame underneath the glass until you see some vapors coming up. If the vapors are dark (should be kinda milky white) then your flame is too hot and try to keep the flame farther away. Make sure your weed is broken up as finely as possible. You'll need to shake it around a bit after each light. When it starts tasting like burnt popcorn it's mostly spent.

I don't know about the toxicity of the glass. I've only smoked out of a lightbulb a couple times, but I think it's just a myth. You're probably fine. You might want to save up and buy a real vaporizer, though.