Here's what you need to do:
1) Slow down as much so you don’t miss the apex and start to drift towards it.
2) Hand-brake can help you reduce understeer (usually on FWD and AWD cars), if it’s not enough, go for the “scandinavian flick”[en.wikipedia.org].
3) Keep your drifting angle as low as possible so by the end of the drift your car is already straightened; drifting is not optimal if you need to “correct” your tail at the corner exit after drifting too much.
4) To chain multiple corners you need to drift all the way through corners without straightening out for more than a moment as the rear end swings around; it’s all about shifting the weight of a car properly to avoid understeer and maintain high speed.
5) Manual gearbox may be a better choice, because auto gearbox tends to shift in the middle of a drift which can interrupt it. Not to mention that you can use a higher gear for more stability (understeer) and a lower gear for high revs and more oversteer.

My controller:
Logitech G27 Racing Wheel[gaming.logitech.com] with manual gearbox.

Harmless mods used:
Solid Carbon HUD mod[www.racedepartment.com].
Raised camera height mod[www.racedepartment.com].