Detect the key of your current song, and pick the next song to be 1 or 2 semitones above it.

If you're in C Minor, your next key should be D-flat Minor (+1 semitone) or D Minor (+2 semitones). Take a look at the image above. The rule is always the same, just go "right" on the piano from your original key.

The effect is really interesting: Energy on the dance floor will rise. It doesn't work with every song, but most of the time it can create a pleasant effect.

Yes. To go up one semitone, add 7 to your current Camelot number. If you're in E-flat Minor (2A), add 7 and you'll be in E Minor (9A).

To go up two semitones, just add 2 to your current Camelot number. If you're in C Minor (5A), add 2 and you'll get D Minor (7A). Play your next tune in 7A, and you'll experience an energy boost mix.

It's better to mix quickly, because the melodies will clash.  You're going for a specific effect, and not a long blend.

I've heard DJ Sasha and Armin Van Buuren use this technique.  Whether it was intentional or not, it sounded great. 

Over 20,000 DJs have read this tip since I posted this tip on the Mixed In Key community.  Mixing +2 semitones is my favorite DJ technique.

Every DJ should try this mix.