When I First started, I watched a lot of tutorials online about proper composition and posing for the model, then it's good to get good subject isolation, usually achieved by a really blown on out background. If you have a low aperture prime, like a 50mm 1.8 or something a long those lines that is ideal for portraiture in my opinion. But if you don't have one of those then try and zoom in all the way on your zoom lens to get optimal bokeh. The lower the aperture the better for that. Another thing to consider is using your flash to get a little twinkle in the eyes.