I did it cold turkey. It took me several attempts over a period of about a decade, I tried the gum and the patch and neither worked. When you take off the patch or stop chewing the gum the nicotine cravings come back. Ultimately you have to quit cold turkey, my advice to anyone is to just suffer through the withdrawal. It gets easier after a month. I quit 13 years ago and I don’t even think about it anymore, and I live with 2 heavy smokers, in fact I quit while smelling and watching them smoke. It’s not easy but once the withdrawals subside you’ll be so happy you did it.
It is very much worth quitting smoking, regardless of what method you choose. Do it for yourself. Do it for your friends. Do it for your family. I don’t know about niacin therapy, but if it works it is probably worth it. I smoked for a couple of years in the army. It took quite a few tries to quit, but I finally did it. Now I’m seeing many people who have had their lives cut short by smoking, and I am so glad I was able to quit.