Don't be discouraged is the first thing I will tell you.
Second thing I will say is, practice, practice, and more practice. Learn as you go and watch others paint. Try and understand the techniques that they are using, and why they are using it. Once I understood what they were doing and why, I then tried what they had done and it worked out.
And because of this reference I have gotten way better than what I used to be.
Shake the paint, I try and shake for maybe about a minute or more. I think that with acrylic you really miss out on so much if you just leave it be. And it has a lot of versatility.
I knot that another thing that helped me was to thin my paints. People will tell you this all of the time, but how do you thin your paints? They don't explain how to do that, so you will end up with runny over watered down paint.
It looks awful.
This is how I thin my paint so it flows nicely. Wet your brush by putting it in water and wiping it off on a paper towel. You might have to do it multiple times. Try to keep it damp. Dip the brush into the paint then dip the tip of the brush, just the very tip, into the water. Then apply the paint to the model moving it around a good amount to cover as much as you can. When it gets a little dry, repeat the process.
Don't be afraid to try different ranges of paint from different companies. I know that when I started painting, I got stuck on a brand. I swore by it, but then I realized that I was really limiting myself.
Protip for the clean freaks: If you are using acrylic paint and you want to remove it, 91% rubbing alcohol will do it pretty quickly. A good scrub with a stiff bristle toothbrush and then a washing will get most if not all of it off.