I'm not very good at drawing (really, but I've improved so I can tell how to improve, maybe!), but I know some artists. They draw a lot. Like crazy amounts.. and they draw everything, all the time, even like when you're watching movie, they're drawing the guys in it. You're probably not aiming to become an actual super artist, so I'll just hint stuff that helped me and hope they'll be of some use to you:
-there's that whole "draw a lot to improve" thing
-look at things and try to see the "curves" (as in "if I wanted to draw that nose, what kind of turns would the line take) and shapes/shades in them. this is a thing that some people I've spoken with have sort of skipped, like this one guy couldn't draw sad faces because he was so used to drawing happy ones that he kept adding the happy features in. if you want to draw a likeness of something, you need to actually look at that something (and if what you see doesn't fit what you're used to, ignore what you're used to, unless you're a boss and have mad skillz, then you can do whatever). also, try to figure out which of the details aren't important
-if you really want to improve, skip the whole "it's good enough" thought that pops up in your mind after you've spent an absurd amount of time drawing an ugly platypus. either keep improving it, or start drawing it again, and do it until you're sick of it. if you want to draw something other than an ugly platypus, well, that's your choice but I don't see why you would want to do that (one of my art teachers made me draw an ugly platypus and it was never good enough; trauma!) :p
-stare at yourself in a mirror and move around to get at least a basic understanding on how a human body works (you need to pay attention too) if you're planning to draw a not super abstract human being. this one's like crazy hard (at least for me, I never got it even though I spent a lot of time trying and read anatomy books)
-if you're trying to figure out how to draw something (that cannot be referenced), try to draw it many times with variations (if you're working on a big piece, do it on a separate paper/canvas for sanity)
Drawing a grid can help a lot with proportions and locations and curves and everything ever (except having gridless pictures :p ). I attached an example of this, which also shows that if you're going to draw with your mouse, you should get a better one than mine. Learning proportions is kind of important, and this can help with it.
Also, this I read on an artist's blog: when you look at someone's fancy drawing, try to figure out why they drew it the way they did, because if you just copy it, it'll always be inferior.