I saw water dropping mentioned.
So, I figured the obligatory warning was in order:
Water is your enemy around a casting pot. If a drop of water falls into your molten alloy, or a wet bullet is tossed into the alloy, the water with flash to steam explosively and spray molten lead all over the place. That molten, flying lead will burn any exposed skin, and stick to it. It will burn your eyes, and stick to them. It will do very bad things to any body part it hits. **
Many casters refer to such events as a "visit from the tinsel fairy" because once it happens, everything is covered in strings, globs, and spatters of lead that make it look like a fairy threw tinsel and glitter all over.
To avoid visits from the tinsel fairy, you must always make sure you're using DRY ingots; not sweating on your tools, bullets, or pot; and make sure that any water-dropping apparatus is assembled or built in such a way as to be below the level of the melting pot, be incapable of splashing, and keep anyone from easily retrieving bullets that might be mistakenly put into the pot while wet. (Most people use angled towels clamped to a bucket, and/or bench in some way. There are many examples on the castboolits forums.)
If you have suspect ingots or scrap, put it in a COLD (or at least empty) pot, and heat it up from there. As the metal comes up to temperature, it will dry any moisture present before getting hot enough for the alloy to melt.
--Alternatively, you could use a separate vessel for pre-heating ingots and/or scrap. My father, for example, used to use a cast iron frying pan on a coleman stove to get his ingots to about 350-375 F, before they went into the casting pot. It was a constant shuffle: Cold ingots went in one side. Hot ingots came out the other, and into the casting pot.
As a bonus, the pre-heated ingots don't take as long to melt in the pot, and they don't drop the temperature of the melt as much.
**There are several members of the castboolits forums that have shared their experiences with tinsel fairy visits that resulted in lead hitting their eyeballs. In every case, the lead caused their tears to flash to steam and offer some protection to the eyeball, but there was still enough retained heat in the lead to continue burning the eye and it didn't do anything for their skin. In ALL cases I've seen, the splattered lead had to be removed from their eyes by a doctor, after an excruciating trip to the hospital.
In one case, the guy couldn't even close his eye. He had a large glob of lead fused to his eyeball and eyelids, and just had to keep squirting saline into his eye during the trip to the hospital, and while waiting for a surgeon to figure out what to do.