Learn first by watching videos, reading articles, and doing ridealongs with people at drift practices. Seeing all the different methods executed in person and in front of you, helps a lot in being able to understand and follow what is going on in the Drift Bible. Learn a lot about how to drift though before you even begin to attempt to start drifting.
Once you begin to first start drifting, as said before, drift on a completely stock suspension. Use an open diff, stock springs/shocks, stock ties, everything. As you learn to get better at drifting and hold your slide longer, and over compensate from the drastic understeer (by using more than three methods!) start to fine tune your suspension a little bit. To get your suspension a little more rock solid in the rear so you have better control of the car's body roll I recommend your first suspension mod being a sway bar. The next mod I would look into are inner tie rods and toe links. These will help you accomplish in getting a bigger steering angle which will play a major roll in getting your car to do feint drifts and quickly lash your car sideways, especially since you will still be on a stock differential. Next comes probably the most important mod in drifting, the limited slip differential. You can just get a VLSD from a HICAS model 240sx (on sale around a lot of forums, and for about $350 or so), or you can get a LSD (name brand diffs which provide for more 'slippage' which will run anywhere from $900-$1500). The (V)LSD will be a night and day difference between your open differential you once had. It will be much easier to execute a slide. Your next mod would probably be to get coilovers. Once you arrive at this point in parts buying though you will have enough knowledge to know what the rest of the mods you need are.
If you have all of the modifications done to your car by the course of one year of drifting has elapsed I will be surprised. Just drifting once or twice on stock suspension and spinning out does not qualify as practice. You should practice maybe once a week if you can for about 4-6 months before you start considering suspension modifications. Then once you begin to upgrade don't buy all the parts I listed at once. Buy them one at a time and learn to drift on them each for at least a month before you start buying a new part for your car, therefore you will understand and really feel the difference each little part on your car makes. Which, in the long run, will help you know what you need to upgrade next and how you need to tune/adjust your suspension in order to be able to drift better.
Taking baby steps like using stock suspension for a while may seem irritating and annoying, but will make you much better, much quicker in the long run and scheme of things. Besides, when you go to drift events you'll be the coolest one there because it will look like you are drifting on monster truck suspension.
Final Thought:
When you have finished watching drift bible enough times that you have it memorized by heart, and have watched a ton of the option drift videos, and you are ready to hit the streets and try drifting remember these few key things...
1. Drift safely. Use an open parking lot with no curbs or light poles that are close together that you can crash into. Also, make sure NO PEDESTRIANS are around! Do not drift on the streets!
2. Be prepared to break something. If you don't crash into a wall, or catch a little of a curb, or just have something break on your car from drifting that means one of two things. (1) You are the next drifting god because you are a beginner and have the ability to have perfect control of the car without crashing or (2) You are driving too scared. It's a very aggressive task you are performing on your car and if you are not aggressive about it, you are not going to break traction to drift, or you only will for a second.
3. Have fun, but don't be a goober. Don't try to show off to your friends and go "look how cool I am" and then endanger the lives of others. Plus all the amateur drifters out there are the nicest, most helpful guys around...that's a nice reputation for all of us to have, please don't ruin it.
4. When you go drifting, always have a friend drive to the spot with you. Firstly so he can be used as a lookout for you so you don't get caught. Secondly so incase you break your car and it is undriveable, you are not stuck broken down in a deserted parking lot by yourself.
That's my little write-up. I'm out.