I STINK at identifying trees! :-(

I STINK at identifying trees! :-(

I've been looking for a good tree identification key.. I have access to a nice Symonds book that I've been eyeing and the Dirr Manual of Woody Plants is also on my 'wish' list.. but i'm looking for something that I can just throw in my backpack, a more high level 'idiot' guide or identification key, specifically for trees in the NE US. (A guide that may have a hackberry for example) Any suggestions? this is the kind of problem I'm having.. I found something that I THINK is a dogwood, but it has leaves with serrated edges. I'm stumped. I know there are 100+ types of dogwoords, but do they have these sorts of leaves???? These are the types of questions I'm facing, kind of 'newbie' ish. I was trying to identify based on flowers but then I saw the leaves... ARGH! Please be kind.. I have not a clue. :( The tree I THINK is a dogwood but with the serrated leaves the full tree and here's one that I THINK is a prunus of some sort.. they're in a very landscaped area, so there's a good chance they arent' native to my area (CT). I feel so clueless. thanks for your infinate patience.
Plant identity question

Plant identity question

Oh, the conundrum….

Oh, the conundrum….

Take a peak!

Take a peak!

Pretties

Pretties

new.

new.

My Yard.

My Yard.