Most Helpful Guy
Go to college, pick a field/major that will help on your LSAT's.
Most people pick philosophy or political science... plenty of other options.
Pass the LSAT's, go to law school and focus in your studies on divorce attorneys then pass the Bar exam.
Not sure what country you're from so they're might be some differences.
Most Helpful Girl
First you need a bachelor's degree. Don't do the usual English History or Political Science, they are useless if your law school plan doesn't work out.
You take the LSAT. Nothing in college will prepare you for that, it tests your logic, reasoning, and reading comprehension. Brain puzzles are the most helpful preparation and their are LSAT prep courses that some people take but they are not necessary. I took them with no preparation.
You apply for law school. If you get in you go. This will be another 3years of school. There is no specializing in a type of law, it is all inclusive. But taking your electives in Domestic Relations related courses is important.
IF you survive the hell that is law school, and it takes a pretty screwed up individual to do so, then graduate and take the bar exam for the state you wish to practice in. The bar is only given in July (starts tomorrow actually) and February.
When you pass, it takes about 3 months to find out, you will be sworn in in your state then you can start practicing.
The biggest thing I can tell you though is you never practice what you set out to practice. There are too many lawyers and not enough jobs. In order to find a job you have to be open to doing what is going to pay the bills. The other thing is law school teaches you nothing about actually being a lawyer, you have to learn that all on your own.