In order to be able to make a good portrait you first need to know what exactly a portrait is. Go search on google on portrait photographers like Erwin Olaf and Anton Corbijn. Look at their work, maybe you can find some inspiration there.
is often more than a nice snapshot of someone’s head, there is a story behind a person. This you try, as much as possible, to bring out in a portrait.
Does someone have a rough life I would make the picture tough, maybe a urban style setting and real hard light (this means harsh shadows). Is someone very lovely I would choose a highkey setting (a setting with lots of bright colors and low contrast). And so you go on a thinking spree, finding new inspiration.
is so that you know your model or know what his or her character. Before you start with making the photos, create a conversation. Also you should listen to his or her wishes, this can make it easier for you to get a nice picture of this person. After all, you have fulfilled the wishes of your model.
part of portrait photography is entirely up to your taste. Do you enjoy much blur in a picture then choose a lens with a low aperture number (F2.8 or below) or make sure to use a telephoto lens (>100mm about may already be really nice) where you can zoom far along. Also, you should pay attention to your surroundings, the closer you are to a background the sharper the shape it is, the further away the fuzzier.
Would you like to know more about the technical aspects, I would suggest you to do a lot of tutorials or follow a (online) course.