Developing interest is the key to enter in this profession. Some people are born with some basic tendency to do or entering in any field but some people need to develop this type of interest in which they think they will be successful. Having a tendency to take good photos is a good thing as you can later on decide in which specific field you want to enter.
Try with basic photos
To become a museum photographer you should try to take basic photos and learn how well you are developing your skills. Slowly take interest in ancient things by reading books and surfing on internet. You will get good information about old museums and places where you can go and take photos.
Take lots of photographs and try hard to learn all the tricks of the trade which will help you in many ways.
Buy a good professional camera
Professional cameras are quite different from general ones. Professional cameras have many other features which help in many ways whenever you take a photograph.
Visiting museums is another important step if you are interested in becoming a professional museum photographer. Many museums have different specialties and you should also decide where you want to go first and expand your experience.