Welcome!
I looked at your portfolio, and I think you're already on the right track.
I'm just a hobbyist too, but here's my tip . . .
Re framing and composition, I've always found that it's important to keep a few simple things in your mind when you're looking through the viewfinder:
1. What am I taking a picture of? I see a LOT of images where I'm not quite sure what the real subject of the image is. A good example of this is people going to a garden and snapping images of a bed of flowers from 3 meters away, then winding up with a picture of a bed of flowers, and no real interest. It's usually much better to find something interesting, like a bunch of flowers sticking up from the others, and then frame so that you subject (the bunch of interesting flowers, within the bed) stands out, both in terms of location in the frame, and ideally separated from the environment / background (perhaps by throwing the bkgnd out of focus with a wide aperture, for example).
2. Use the rule of thirds. Put your subject on one of the imaginary lines that fall at the 1/3 point in height and width in the viewfinder. This is particularly important for images of people - you want the eye line roughly to fall on one of the third lines. I see from your portfolio that you're doing this pretty well, though not always. Of course like all rules, it's not appropriate for every situation, and sometimes an image is just better with the subject perfectly in the center, but when starting out you'll usually find the rule of thirds helps you make better pictures quickly.
This is what I mean (Hope you don't mind that I've reposted an image from your flickr. If you object, I'll take it down):
I like that you left a lot of space around the dog, creating a sense of interest, but it might have been even more interesting if the dog was on one of the third lines.
3. Check each corner and edge of the viewfinder before you press the shutter, and be sure that what you see there is really what you want in the image. If not, recompose. The idea is to not just focus on the subject, but make sure the subject's surroundings aren't too busy, and you don't have any arms/legs/trees/etc hanging into or out of the frame.
My 2c. Take Care,
Eric