It is important to note at the onset that you need to choose one primary photography category and become skill full in it. Though many different offers may come your way, you slowly need to build your business around some primary goals. Are you doing portfolios, or are you doing families? Will you go outdoors for a shoot? The reason for getting to know yourself what you want to do and what you are good at is that focusing on one aspect will lead you to improve your skill level in that area, gain recognition and produce high quality repeatedly. You will become expert in few, and probably master in one.
It is all right when you are starting out to experiment with all these. In fact I encourage you to experiment with different kinds of photography. When you see the results, some you will like, and with some you will be disappointed.
Some skills you will pick up naturally and some seem hard needing a high learning curve. You might find you are good with kids, and can make them playful and relaxed in a photo shoot. Or you are the loner type who would rather spend nights shooting inanimate objects. Your personality will ultimately dictate the type of photography you will take up.
That is part of the learning process. Focus on the ones that you don’t struggle with. If you are just starting out the process will help you find out your strengths and weaknesses. It is better you take time to find out what you are good at, than years later after substantial investment in time and money.
Another aspect of deciding on what type of photography you want to do is about investment. Each line of specialization requires its own skillset, equipment, lighting equipment, lenses and attitude. After spending thousands of dollars on studio setup, you may then realize that this was not what you had in mind. Yes, you can start all over again, but you end up losing time, money and motivation.
Unless you are sure, and believe me, many photographs do know what they want to do, experiment. You want to do a portfolio? Hire a studio space for half a day. Take two friends for a test shoot. Bring your camera and lenses, the rest of the equipment like stands, strobes and backgrounds are often included in the rental, or available at the rented studio for an additional low fee. It is perfectly reasonable to ask for help from the staff if you do not know how to set up the lights and trigger the strobes. If you tell them in advance, someone will surely be able to help out with the technicalities. Spent couple of hours shooting your friends, and pour over the images. Some of them look promising? Go back next weekend and repeat. You will soon find out if you want to invest in a home studio, or are just fine with renting one when required.
Choosing a stream and focusing on it is probably the best approach once you have tried on different options. There is lots of free material on the web to pick up and learn. Step by step YouTube instruction videos are a great help. Buy some photography books (See the section on Resources). After all this watching and reading, the best way to increase you knowledge and skills is to practice.