Lubrication the drill-bit must be lubricated and cooled all at the same time the best way to do this in a household situation is to make a mixture called an emulsion. This is a mix of oil and water and is used in steel cutting.For home use 2 parts water and one part olive or rape-seed oil and add a little dish washing liquid about tea-spoon full. Mix together by shaking vigorously in a discarded dish washing liquid bottle. You can use the bottle and nozzle to apply liberal amounts of the emulsion to the drill while drilling. (I know some machinist that use only the green colored dish washing detergent).
Remember, type of matl. and thickness play an important role and, Generally speaking, the smaller the drill the faster the speed. The larger the drill the slower. I say generally because when you start drilling some of the exotic matls. ie: Titanium as well as others, you could "work harden" the material by using to many rpm's.