Ok, to start, the onboard flash of pretty much any camera is the debbil, so you are right on there.

Natural light all the way, baby!
I'm not the best in the world at giving critique, but I'll do my best.
The first one is a pretty great pic....that could be even better. You captured a wonderful expression, which, that in itself can be very challenging. Overall the shot seems a bit overexposed...white fur is hard to expose for. I think it could have benefited from having a background that contrasted a bit more from his (her?) fur, as well. One other thing to point out is the chopping off of the ear...either include the ear, or crop with purpose.
There are a few of the same things going on in the others...such as #3. #3 is a REALLY difficult exposure, because the one thing that is as hard to expose for as white fur....is black fur...and that pup has both! If you noticed, the white spots on him are REALLY white, with no detail....again, over-exposed. However, I wouldn't underexpose that one TOO much, as you risk losing detail in the black....this is a case of trying to find the middle ground...may not be easy or even possible to get a perfect exposure on that.
Also on #3...and #5, you've got a bit of close cropping to watch out for.
I'll comment more fully on the rest of them if you'd like me to later...for now I'll step back and let someone else agree/disagree/add to what I said.
I will say that I don't think it will take you very long to pick this up. From seeing your other pics, I know you have a creative eye.