Cram for the test, not the content, much of which is largely arbitrary, arcane and will almost certainly never come up in your experience. If there's any future doubt, you should certainly reconfirm stuff at the time you need it in any case, because rules and practice will change during the span of your licensure anyway.
This was the advice I got, and having just passed Technician and General last week, I absolutely agree with it. I have a long professional background in practical electronics and broadcasting, so much of the useful stuff I already knew. A number of answers I tend to disagree with and I didn't really need to know about music to the Space Station or the invocation of the War Powers Act, etc. Still, I learned some stuff that was interesting and occasionally useful, particularly about antennas. So, use common sense -- if it sounds like something you'll need or seems interesting, study it. If it's just fluff that will never come up in your lifetime, remember a keyword or mnemonic in the right answer and move on.
Check your library for the latest study guides. I was able to get the current ARRL and Gordon West books (through interlibrary loan, as it turned out, because all the local stuff was outdated) for both Technician and General, and didn't have to drop ~$120 on them, which I wouldn't have in any case. Free is better.
I have mixed opinions about which brand was superior, so go for what you can get. The ARRL book seems to me to be unnecessarily intimidating and initially scared me off for going for General. The West book cured that as it's based on the premise that any reasonably bright person can pass the test, which is absolutely right. The sole advantage of the ARRL book is that it has the entire question pool conveniently placed at the end, which is a great tool for just scrolling through with your thumb over the right answers. That's the best way to learn, once you understand the basics.
One big caution: I think the online moot tests are really defective because they post the questions pseudorandomly, which means that you can take them fifty or a hundred times and NEVER see some of the material, while other questions are seemingly in every single test. I can't understand why there aren't however many of fixed tests there need to be to include all the possible questions and then you can take them in sequence. This problem will definitely come back to bite you on the butt.
I took the online tests from all the various sites at least a hundred or two times for both Technician and General and could reliably score 96%-100% on both, but when I took the Technician test, the first two questions were ones I had absolutely never, ever seen on these tests and did not recall from either book. I figured them out, but it was still just like that moment in the classic nightmare! Kinda shook me up there for a second.
I would not consider going to a class for this stuff. I'd sooner die. You may of course feel differently.
Frankly, this whole exercise -- the real test -- was simply to see if my old brain was still working. Successfully memorizing a pool of around 920 questions is pretty indicative of a still-functioning mentality, so I'm chuffed. I suspect this motive is behind many of the new candidates; at my test session, there were around a dozen and only two looked to be substantially under seventy. I was shocked. I thought all hams were old codgers, but started when they were in Boy Scouts.