How To Make Crack (common method)
This is the most common method. Get a spoon and mix 2 parts of cocaine hydrochloride (regular cocaine) to 1 part baking soda in some water.
Heat solution gently (with a lighter or candle) until white precipitates form, and stop heating when precipitation stops.
After gentle heating, the freebase cocaine will float to the top, any excess soda will settle on the bottom.
Collect the compound that rises to the top, and you have the finished product, ready to use.
What you're trying to do is start and sustain a chemical reaction (bonding the hydrochloride with the base-soda) so as long as the reaction is happening you don't have to continue heating.
How To Make Crack (uncommon method)
I've never seen anyone try this method. You make crack as described above, then wash it with water and allow to dry for a day.
Mix 2 parts of cocaine hydrochloride to 1 part baking soda in some water. Heat solution gently until white precipitates form, and stop heating when precipitation stops.
Collect the freebase cocaine that floats to the top.
Wash freebase once with water (this procedure usually omitted in street product).
Dry 24 hours under heat lamp (this procedure usually omitted in street product).
How To Make Freebase Cocaine
Crack cocaine is less pure than using ether to make freebase cocaine, but the procedure itself is safer than using this method.
Mix about 1 gram of coke and 10 ml of water in a small vial. Slowly add drops of ammonia to the solution. A white milky precipitate will form. Stop adding ammonia when additional drops no longer result in precipitation.
Add 5 ml of ethyl ether, close vial, and shake. The precipitate (freebase) will dissolve in the ether. Siphon off the ether with a pipette (ether and water don't mix), and slowly drip it on a plate.
As the ether evaporates, white crystals will form. This is the evil freebase. Crush the crystals and put under a heat lamp for at least 24 hrs to let the solvent evaporate.
ETHYL ETHER IS EXTREMELY FLAMMABLE. IN THE PRESENCE OF AIR IT CAN FORM PEROXIDES WHICH WILL SPONTANEOUSLY EXPLODE! ALSO, ETHER CAN CRAWL FROM AN OPEN BOTTLE AND TRIGGER AN EXPLOSION MANY FEET AWAY.
This is how Richard Pryor almost died. A lot of untrained people killed themselves doing that procedure, and this is why crack is now more popular.