Nicotine patches helped me to quit.

On my GP's recommendation, I started of on a fairly high dose and tapered off slowly over some months.

The other thing which helped me was to keep track of the money that I have saved by not smoking.

Every so often I did (and still do) give myself a reward with some of that money - a nice restaurant meal, a book or DVD that I have always wanted, etc.

That helps me to stay motivated.