Uh Oh, here's a force coming into the mix! Dan, those are most excellent first doodles.
I'm already excited to see your own gallery thread coming and growing!
Your proportions seem already quite advanced and not at all troublesome. But I did make a little showcase at some point, doing the Spock portrait a long time ago by now. (AH, I FOUND IT AGAIN:
viewtopic.php?p=5097#p5097 ) However, there's endless material on the web, of course.
My own technique is that of relative observation, also always happily considering Fibonacci and the golden ratios. I've noticed that you can almost rely on a certain "DNA", which manifests in deviation of the gold ratio and it tends to hold true throughout the entire body and every detail. With this in mind you can create your own kind of reference ratio for any individual face, for example. See which two elements are meant to be in this kind of ratio and also consider fractal repetition of this. For example: size of the hand to the root of the fingers, length of the fingers to the knuckles, length from knuckle to tip compared to root of the nails. In a face their our countless such relationships.
As for perspective, well, you have to develop a feel for it, which you get to via understanding, of course. But understanding is much easier than getting the feeling for it. The trickiest thing, which people often forget, is the lens distortion, which is highly relevant to really arrive at a good use of perspective. None of it is rocket-science, but it does take a great deal of practice and careful, conscious observation.