There are enough different techniques and enough different equipment out there for casting to write a book, and while everyone may have a little different "right" way to do it Three things come to mind that are (or should be inviolate)
1. hot lead
2. hot mold
3. clean lead.
i dont use a thermometer, and just run my lead hot enough it starts to get that blue/yellow coloring on the surface and i dip my mold into the lead and when its hot enough lead of the proper temp does not stick to it, that brings the mold to about the right temp. then reheat the mold as necessary if i start to see some flaws in the balls i'm casting.
before casting anything, i get my lead clean. i smelt and flux it sparingly with beeswax, or a bit of old candle (though many other things work well too) and skim off the dross.
get a technique down & with what i said above, you'll be casting great balls or bullets in no time.
one last thing is have a good pad to dump your bullets out on to. i use the leg off of an old pair of jeans folded over. and pour enough in your mold to have a good sprue, at the proper temp your sprue will take several seconds to solidify.
on a safety note: cast in an area with plenty of ventilation, many people keep a fan blowing so lead fumes drift away from them and keep liquids away from molten lead. it will literally explode out of your pot. (ive never had that happen fortunately but i did see a video of it one time, under controlled conditions.)