Best way for a middle-ager to prep for the GRE?

I’d do a search on the internet. There are lot’s of study materials for all kinds of standard tests; some free, some not. May not be difficult to even locate old tests with the answers.
Try this google page Google

Should have added: At your age, you are likely to know more now than you did earlier. But since you’ve been out of the testing game for a while, self-talk is really good.

I recently started grad school, and some schools wave the GRE or don’t consider it as heavily if you have considerable work/career experience (such as yourself). I would talk to the admissions people at the schools you’re interested in and express your concerns over the GRE and see what they have to say about their requirements for applicants such as yourself.
If you do end up needing to take the GRE though, just remember that on the math portion it’s all about recognizing what they’re asking you for in the problem, and then estimating the answer. They don’t expect you to solve every problem (obviously it’s impossible in the time allotted and without a calculator) so you have to get good as getting it down to 2 answers and then guessing between those two. This method worked well for me.

1. Take a practice test so you know where you stand rather than trying to guess. I was a GRE (/SAT/ACT/SSAT/MCAT) tutor for a few years, and people often overestimate their weaknesses. ETS will send you two free practice tests.

1.5. Find out what score your programs want you to have. If a 1000 will cut it, don’t drive yourself nuts shooting for a 1500.

2. Buy a bunch of prep books from various companies. Different strategies will work for different people. Try them all.

3. Create a study schedule. (I would be happy to help you with this after you take your practice test!)

4. Practice! You know your study habits better than anyone else, so you probably have a good idea of what works for you. My general advice is: start with your weakest areas, and as the test approaches, shift your focus to things you’re more comfortable with.

5. YOU CAN NEVER KNOW TOO MANY VOCABULARY WORDS. Seriously. I thought I knew enough. I was wrong.

If you can get your hands on more practice tests, I would encourage you to use them, but use them to practice your timing and endurance rather than as score predictors. The tests written by companies like Kaplan and The Princeton Review tend NOT to be accurate predictors, but they’re still solid practice.

The more of these you take, the better prepared you will be for your actual test, especially if you can simulate a test-like environment. (Silent, no calculator, taken all in one go, 6 sheets of scrap paper.)

If you want specific advice on how to approach different question types I would be happy to throw some of that your way too. Feel free to message me or girlofscience, who beat me by a full 70 points on the math section. I’m sure she’d be happy to help.

Are you taking the general GRE? From your question that’s what it sounds like, but you want to be sure. There are subject specific GRE exams that some departments require.

Do find out what scores are usually required on which test for the program you want to enter. They may phrase it as “last year’s new admissions scored….” The scores they accept will often change a bit from year to year depending on the competition for the slots they have in that program each year, but the numbers they accepted last year will give you a ballpark. Also, if you’re planning on getting a master’s in creative writing they’re a lot less likely to care about your math score than if you’re going into engineering, physics, or math.

Niki had some great advice above. I’d add that a book with a CD that mimics the test environment is a good idea, too. I had a good experience preparing with the Baron book for the general test, and the REA books for the subject specific tests.

@Kay: It’s not impossible to solve every math problem without a calculator in the alloted time. It just may matter more or less depending on your program.