If you know anyone who does any DJing, the best way to find out what it's all about is by having a go. I tried it out for the first time many years ago when my sister got into it, once I had a go my indifferent to dance music was broken. Although DJing isn't one of my hobbies, I'd say mucking around with it has helped me gain an appreciation for a huge area of music I previously ignored. I am now very interested and try and write tunes myself.
The first thing you learn to master is beat matching; you'd find this hard at first. After that there are loads of techniques, ranging from simple to complicated, that DJs use to make the mix interesting (new technologies are always adding to the kind of effects you can achieve). I think you'd find that good DJ's have great knowledge of their records, what songs work with one another and structures of the songs - you've got to know where to start a mix and where you can mess about with the record.
My friend has just bought a mixer that has a function where you can sample the record as it plays and loops this over and over again... actually here is a tutorial from youtube:
YouTube - Pioneer DJM-800, Assign Roll from one channel to another
Those are some of my thoughts on the subject. DJing can be as complicated and interesting as you want it to be.