+1 on the great advice already given. To answer a couple more of your questions, your alloy temperature will affect your boolit weight as well. You typically want to cast with as low a temp as you can still get good mould fillout with. A lot of people find 600-650 degrees work very well, but some moulds like the alloy a little hotter, some as high as 750.
If you are melting down wheelweights, keep your pot temp below 700* to avoid possible zinc contamination. One Zn weight will ruin an otherwise perfect pot of alloy.
When casting, I find a hotplate next to my casting pot a great advantage to keep the moulds up to temp and reduce the number of rejects when starting a casting session.
One last tip... Bullplate sprue plate lube. It simply works!