The first step in a long-distance master's degree is to find the right school. The Department of Education's accreditation database can be a good resource to make sure that the institution you're considering is reputable. In many cases, a better option is to look for traditional schools offering long-distance degrees. Many established schools, recognizing the need for continuing education, now offer online or long-distance degrees for working professionals.
Don't make the mistake of assuming that a long-distance master's degree will be any easier just because it's online or carried out at a distance. The workload --- including extensive reading, analysis and writing --- will generally be similar. In some ways, in fact, distance education is more difficult --- you have to be self-motivated, for one, and you don't have the option of immediate face-to-face contact with your professors. The trade-off is that you can study while continuing to work, and in many cases you can pick your own hours. Consider carefully whether this is worth it to you.
A long-distance master's degree will generally involve course materials that are delivered over the web. You may have a fixed lecture period in which you log in to a live, streaming broadcast of the course --- this will allow you to take notes and ask questions, and is most similar to a traditional classroom. On the other hand, all materials may be delivered without live instruction, meaning that you'll have to figure them out on your own.
Like a traditional master's degree, a long-distance graduate education will generally require a capstone accomplishment. For academic programs, this may take the form of an online master's thesis. For other fields of study, like an online MBA, you may be required to complete a final project. In some cases --- for instance, in final projects involving group work --- a long-distance master's degree may require you to spend a few days on the school's campus.