From CoMakingSpace Wiki

Calculating the proper milling feedrate ("travel speed") is crucial for successful projects and a long lifetime of your end mills. Check out this English tutorial.

Problems will occur if your speeds are too low or too fast for the given tool geometry and material, so it's not advisable to start very low and "sneak up on the ideal" like you might try when laser cutting. The proper combination of spindle speed and feedrate is especially difficult to dial in if you just guess around, costing you tons of time and material...

Example Parameters

We are collecting our experiences with different settings in this wiki, and some machine or bit manufacturers also publish tried & tested values that might make your life easier.

Keep in mind that other people's experience with different machines or endmills/bits is always just a starting point to dial in your setup!

Interesting resources for our WorkBee:

Feeds and Speeds Calculators

Manufacturers of quality endmills usually supply the tool properties you'll need to calculate the proper speeds and feeds with a couple of formulas. This PDF by Sorotec (DE) explains it nicely.

Of course there is also software that can do this for you (please share your experience):