[Kraftwerk]

Cutting fluid is essential and it smells like root beer!
If you are cutting circles in metal: Buy these fantastic hole saw drills manufactured by Relton in the good old USA Arcadia, California
(American made quality goes a long way to getting the job done quickly and neatly, don't get me started on Chinese crap!)
They are not cheap but the only thing I will use.
This company will also restore, sharpen and re- tip your Relton hole saw bits for a small fee.

As far as drilling goes: the proper RPM and the right pressure is important, also the tool should be 90 deg. to the surface of what you are cutting.