What I highly suggest is watching some people drift on GT5 on youtube, it gives you more of a feel on what to do IMO. You see how and when they take corners and you try do what they do which kind of helped me anyway.
I would also recommend not tuning cars at all, because for me, leaving a car stock and slamming some Comfort: Hard tyres on is better than any 'tune' itself.
This is just my opinion, I genuinely started drifting 2/3 days a go and I'm pretty good (not being big headed).
Definitely would recommend watching people drift though, as it helped me so much.