Why tin? Tin melts very low in temperature. Basically, the lowest melting point of any useful, non-toxic metal(*). It melts around 500 degrees, is very castable, and looks brilliant. There's only one real good reason not to use it: it's relatively expensive. I got mine from Rotometals in San Leandro for around $10/lb. Its density is similar to lead.
(*) Tin may cause some illnesses, this is debated. work it as if it does. Do your own research.
Step 1: Safety!
Tin is cooler than basically any other metal you'll ever work with, that means that if you screw up, you'll probably survive and have to deal with the hospital, burn wards, grievous scars, and potentially being disfigured or crippled for the rest of your life. Always have full face protection, arm and body protection that buttons at the neck, and closed toe shoes.
Respirator might not be a bad idea either, as who knows what those stray 1 or 2 percent are in the 98-99% pure Tin. I suggest doing things outside.
Pretty much, dress like you're welding, only with a clear visor. Check out my fashion statement picture for an idea. Do any of this at your own risk, perform your own safety assessments. Only you are responsible for the consequences of your actions.