I use my deer fat for patch lube in shooting flintlocks, but that uses maybe an ounce a year. Most of my deer fat gets rendered out for making soap.
Like Hawkdancer said, I put the finely minced or ground deer fat into a large kettle of salted water and let it boil away for hours and hours. Do not run out of water, or it will burn and give your rendered tallow a strong stink. The whole mess is strained through muslin cloth and set outside on a cold night to set up. The fat floats, turns hard and is paper white, with very little odor.
The solids you strained out with the muslin fabric can be put in a roasting pan and popped in the oven at 210-220 degrees F to further render out. But this fat will be darker and have a stronger smell. The less meat and connective in the fat, the less odor/taste/color you will have in the final product. Fat that is liquified by frying has been "tried".
Once it has been tried, and the last solids strained out again, you can put the fat into a pot of water (preferably more water than fat) and boiled for several hours to clean out some of the stink and impurities. It cleans up a little, but it won't be the white, nearly odorless stuff you get the first time through.
This gives you two grades of rendered deer tallow. If I had to eat one, it would be the first batch rendered by boiling. But I have access to pork and beef fat for making sausage, and chicken fat for frying (Oh baby, taters fried in chicken fat...he'p me Lordy!) I will use the finer grade for soap, and the lesser grade for patch lube, leather dressing, etc.
