For me, snaking came natural. I own all the previous Mario Kart games, and for me, it only makes sense to boost as often as you can on a track. I really have no love loss for the people who give up the game because of snaking. It's not even something you can draw a line with. For example, when I can I use boosts? Just once per turn? Can I boost going into it or coming out of the turn? It's just too hard to define where this technique begins. All that aside, the designers intended to put snaking in the game, so if you don't like it... um, play Tetris? :-"
Anyway, simply put, snaking is just boosting back and forth on a straight, wide path. It's fairly simple to do on most online-available tracks -- even more so because it's always 100cc online. My tip for those of you who haven't got it down yet is to try and get the red sparks as fast as you can. When I miss a boost, it's usually because I didn't get red sparks soon enough and I have to drift hard back on track or risk boosting right into a wall. Get those red sparks fast, go back and forth drifting continuously, and you've got it!