Smoked a few with my younger sister in my early teens but didn't start properly until I was 18. No one pushed me, I just decided to do it and pretty much got hooked from the start. Didn't hit a pack a day until I was in college living away from home though, I came from a heavily anti-smoking household and we weren't allowed smoke in view of our parents until our 20s! Very quickly I was up to two packs a day and stayed on that until about two years ago when I cut down to a pack and a half. Haven't smoked indoors in 5 years, my wife got really anti-smoking when she got pregnant with our first kid and has had me smoking outdoors since then.
But, she really approves of vaping so I get to "smoke" at the PC again which is a lovely feeling to have back! Being able to get my nicotine fix without having to wait for an ad break or similar is wonderful!