I recommend learning the basics first before attempting DDT, it's a technique that's only really used by the players at the top of the ladder. Judging by your current P1 time you've still got loads of room for improvement on stuff like straffing, cornering, efficient use of boosts etc.

Once you start hitting top 50 times might be a better time to consider DDT. There are some useful guides in the Articles section of the site.

If you're really set on using DDT straight away, I guess BPA or Yazzo are probably the best to reply.

Ok then, I was somewhat under the impression more of the higher times where using the DDT. I'll work on the basics more then. Hopefully I can find my old gameboy... the gamecube controller is just not that precise, keep hitting L+R during turns when I don't want to.

 DDT is not simple to be used... 

I reccomend you to start with simple circuit (B1 or Q1..) at the beggining mybe you'll bump a lot of time against the wall, but if you try a lot you can dominate this technique... Of course you have to use this technique a lot to master it right... I hope to see more your improvements!!!

yes, I agree with you 

The principle of the DDT is to get sideways and hold the opposite shoulder button to add the strafe speed to your total speed. So if you're steering to the right and hold L you will strafe in the direction of travel and the top speed will be higher. Hold the drift as long as you can then release L and steer left and hold R. Repeat this until you run out of track! Note this is only for use on long straights and you will need to practice how often you can do this before you hit the corner.
 

As a previous poster mentioned, you should master strafing first, hold the shoulder button and steer slightly to correct and your top speed will increase (although the speedometer does not reflect it). When you do this you get the additional speed of the strafe, but not all of it as not all of it is in the direction of travel. The DDT allows you to get almost all the strafe speed.
 

Source: I spent most of my adolescence playing this game.