Like with all the other stuff, you get what you pay. The best turntables you can get are the Technics SL1200/1210/M3D. They are the standard in clubbing and hiphop right now (but there are serious contenders coming up like Vestax and Numark). Get some slipmats (to keep your records from damaging when scratching). Then you need good cartridges too. I can only recommend you three brands : Stanton, Ortofon and Shure. If you're into pure scratching I recommend the Stanton 505SK, if you like plain mixing too, I strongly advise you to take Ortofon Concordes. You'll also need a good scratch mixer. The absolute best here are the Vestax mixers, but they are very expensive. Technics and Stanton have very professional scratch/battle mixers too, but still at a high price. You'll need good headphones to cue your records. I suggest taking the Technics RPDJ1200, but the Sennheiser HD25 and Pioneer SEDJ5000 are excellent too. But again they are pretty expensive.
Normally you'll need an amp and some speakers, but to begin with it's good to connect your equip on your hifi.
And of course you need good records, forget cd's for scratching, only one cdplayer can scratch decently and it is way too expensive!!!

Off course a beginning dj will never have enough money to buy this equipment (unless you're a rich guy). So it's better to start off with some cheaper equipment. One warning : NEVER, NEVER take belt-driven turntables. Always go for the direct drives, as this is important for mixing, but yet more for scratching (higher torque so the platter takes less time to get at speed again). Gemini and Numark are good brands to start of with, their prices are very competitive and the quality is rather good. But as soon as you can, upgrade to Technics or Vestax turntables, because it will be muxh easier to expand your possibilities with those TT's. Same problem for the mixer. Again Gemini and Numark are good brands to look for. If you have a store nearbuy, ask if they have demo equipment. It's always better if you can test the equip. before you buy it (believe me if you don't you could have nasty surprises). Buy whatever you are most comfortable with (and of course what's in your budget range).

So once you got your equipment, adjust everything properly and then learn how to use it first, before attempting to scratch. Then you can begin to perform some basic scratches. I'm not going to explain them here, because I'll still be busy next week then, but there are some good sites about that matter (don't know them anymore right now, but I'll look them up for ya).
But don't think you'll be like Jazzy Jef or Grandmaster Flash in one week. Mixing and scratching take years of practice to be good. You must be dedicated to what you do. If you want to dj to impress your friends, forget it. You must love what you do. The only way to get better is practice, practice and practice (oh and I forgot practice too).

If you got any probs, ask...

Peace
Dj Thy