Quitting Smoking "Cold Turkey": how did it work out for you and what advice would you give?

my friend is quitting both smoking and chewing tobacco, I suggested since he is unhappy with his gaining weight that he take up working out as his new habit. (maybe even get a trainer to help) He hasn’t gone a whole week yet and he’s already feeling anxious and irritable. How can I help?

( I’ve been a non-smoker for 12 years now and I’m in pretty good shape- I actually pass for much younger- I credit stoppping smoking (and drinking) for part of that.)