Get a cheap controller and have a play. I recommend the Numark Mixtrack III [1] because it has an audio interface built in. I think it comes with Serato software, but you could download a trial of Virtual DJ [2] too.

The software processes your mp3's to detect bpm. You then select songs with similar energy and sound (this is what I feel makes a great dj), match the bpm's together and then using the headphones to cue play them together in sync and then using the fader you bring the other track in, then at some point fade the other track out.

Advanced things to do are: 1) Loop the outgoing record - most dj software allows for a single button to select and loop one bar. This allows you to mix without worrying about the old song running out of time, and/or lyrics mashing over one another. 2) Harmonic mixing.

Obligatory Plug [3]

[1] http://www.numark.com/product/mixtrack-pro-3 [2] http://www.virtualdj.com [3] https://www.mixcloud.com/ddmfhsuk/june-cd-swap-bonkers-mixta...