Whether it's to get a GED or a Ph.D, going back to school after 15 years can be a harrowing experience. You've been out of the educational groove for such a long time that it can be hard to regain the necessary skills. On top of this, you're likely entrenched in "real life" issues, so you may have to make sacrifices you didn't have to make in your younger years.
Make a Concrete Plan
At this stage of your life, you most likely don't have the luxury of time to "find yourself" in school, dabbling in a bit of this and a bit of that to see what you like. Ultimately, your main reason for going back to school is to improve your life. Do your soul-searching ahead of time and then search for schools that fill the bill. For example, if you're a high school graduate who wants to get into health care, a two-year program might be the right fit. If you already have a college degree, but want to change careers and become a teacher, you may need to take a few courses in educational theory to prepare for the licensing exam before heading to a master's program.
Figure Out the Logistics
Think about the life you currently lead and how it will fit with being a student. If you work full-time, you might only be able to take evening classes, which means you might take longer to complete the degree than a full-time student. If you have kids, you may have to juggle your schedule with a spouse or a babysitter, or you may only be able to take courses that fit into your limited schedule. Despite these challenges, it is usually still worthwhile to go back to school -- so make plans, set your goals and stick to them.
Non-traditional age students still qualify for federal student aid in most cases. Along with your school applications, fill out the Free Application for Federal Student Aid. This will take your income into consideration in financial aid decisions. Resist the urge to take on hefty student loans, especially private ones. Your job prospects may not be as great as the college marketing materials suggest. It might be better to take fewer courses at a time, using your current income to cover a portion of the costs of school.
Manage Your Time
Determine when you study best. If you work all day, then come home to make dinner, help the kids with homework and get them ready for bed, you may be too tired in the evening hours to focus properly. Instead, it might be better to go to sleep early and wake up early. If your area of study is something that will help you advance in your current career, such as earning a degree in computer programming, your employer might allow you to spend some time at work studying, provided you don't have more pressing work assignments that you need to complete. You may not have a lot of time for repeated review of your schoolwork, so take good notes the first time you are introduced to the material.