For me, it was a month-long phasing smoking out and vaping in, a little at a time -- I kept a tally of cigarettes smoked, and really enjoyed watching the tally-marks get less and less each day that went by. Mainly because when I first started, I really had no thought of quitting smoking, I was just trying to cut down, and not have to go out in the cold (it was Feb at the time). It surprised the hell out of me that I was able to reduce it so much that quitting became a real possibility, and then a fact.
And that technique actually worked for me twice -- after my appendectomy when I went back to smoking, I did the same thing, and was able to keep the return to smoking down to just a month, by gradually increasing my vaping each day. Once I get to about 5 cigarettes a day or less, they just taste awful, so it's not really hard at the end.
Andria