What keys to start a mix with?

[DJ Nada]

If you don't know what a key is you shouldn't be asking questions like these. Go buy beginners guide to music theory and get stuck in.

If you want to be a professional at this craft, learn a little music theory. DJing is like playing an instrument.

It doesn't really matter what key you start in. (Kinda) A major key gives you a more happy, full sound, while a minor key will give you a sad, scary, or serious sound. Think of the Barney song compared with the Jaws theme, quite different, right?
That said, just pick a song that sets the mood you want in your mix, and AFTER that song, you can start worrying about if the key of the next song matches up.

[B.Hallowell]

Maybe this will help and solve some answers?

http://blog.dubspot.com/harmonic-mix...j-endo-part-1/

[padi_04]

Unless you are "keying" your tracks manually, don't stick so rigidly to keys, software ain't 100% correct.

Pick a nice intro track or make one and take keys as reference, but be open to "break the rules" a bit.

[BradCee]

balls to the key, just smash tracks together during drum solo bits