I'm only on day three with my 510, so I'm still trying to figure out the same thing.
What I have figured out is - if I put on a cart (I like the straw-mod) filled with 26mg (and I usually drip 2-3 drops on the atty when I swap out carts) I don't really "chain toke". I'll take a couple of good draws and put it down for a bit.
With an 18mg pre-filled cart, I can hit it a lot more frequently (a mental thing? perhaps because I know in my head it's lower mg?) I am trying to be aware and figure it out because I'm still learning, but I do know I really like it. I enjoy this so much more than my cigarettes, which is weird - because I had such a strong love/hate relationship with my cigs.
I know I do like to just sit with the tip in my mouth between my teeth. Last night I noticed that I'd really beat up one of the cart tips by biting on it. Today, that marked up bitten on tip is for some reason my favorite. It feels like mine, it's comfortable, and I'm still biting it.