Pick a tree, put your talent points into it... all of the warlock's trees are good for leveling. We're not a defensive class in any way, shape, or form, unlike, say, warriors or paladins. I personally would recommend against taking destruction right off the bat (it's a rather inefficient build, mana-wise), but I know folks who WOULD recommend a destro build for leveling, so...
As for 70... Well, maybe you should worry more about leveling for now? It'll take you some time to get up there, and it's easy enough to respec later (it does get a little pricey, but I see you have two 70s, so money shouldn't be too big a problem).