I smoked for about 23 years-- tried to quit more times than I can count (patch, gum, hypnosis, accupuncture, etc.). Truth is I just had enough and realized I was turning 40 this year and it was time to give it up.
I quit cold turkey for a couple days, then chewed Nicorette for (low dose, about 6-8 pieces per day) for about three weeks. Got a prescription for Chantix to help get rid of the anxiety with stopping the gum. Now I've been quit just shy of 6 months and haven't felt better in years.
The key is to want to stop smoking 1000 times more than you want that cigarette, do it for yourself, and never take another puff.
As for your friends that smoke-- just show them how it is to quit. I would bet you money that every one of them wants to quit at some level, but isn't quite ready to make the plunge. You do this, and you could be the trendsetter in your circle of friends. And if not, you'll still feel better, smell better, and it should help your workout since smoking decreases your circulation.
Excellent decision-- one you will absolutely never regret.