This app was mentioned in 9 comments, with an average of 2.22 upvotes
This is kind of obvious but: download a dictionary app to your phone. The merriam-webster one is free, takes about 40mb, and works offline. That way you don't ever have to skip over a word you don't know - whip your phone out immediately and look it up. The process of typing it in and defining it will probably help you remember it.
There is a vocabulary builder app, but I've never personally used it. Good ratings though.
You can also check out /r/logophilia, though for obvious reasons you will mostly end up learning obscure, niche-type words.
Speaking of: merriam webster does have a word of the day page you can check, which is often quite interesting.
Now a word of warning: I spent a large part of my life learning all the words I could and applying them to my speech. Later on, in my adolescence, this lead many people to view me as pretentious. So when you learn all the new fancy words, be judicious about their use! And don't be afraid to mix them with a fair amount of colloquialisms.
Hey, sure. Nothing too complicated. But I'll post a detailed answer here and hope it helps. Obviously this is a subjective answer based on my own strengths and weaknesses. As it happens, I found the verbal section easier given the sparse competition at the higher end of the curve, while the quant was more tricky because many more people do well in quant. Therefore, margins for error are very small.
I did not pay for anything except books (no online resources other than youtube). Retrospectively, I'd say the following resources proved super useful:
The official ETS GRE book + Verbal & Quant Workbooks.
Manhattan Prep's 5 LB. Book of GRE practice problems
Either Magoosh's 1000, or the Barron's Essential 800 word list.
And that's it! For the AWA section, reading sample essay responses online and using youtube videos etc. to form a strategy to approach issues and arguments is enough. Although admittedly I haven't received my AWA score yet, so.. but it didn't seem to go badly.
The 5 LB book may not be ideal for verbal practice, but it is brilliant for the quant section. ~23 chapters full of problems, solutions, and explanations. My strategy was to see the number of problems in any particular section, multiply by 1.4-1.5 and set a timer for that duration. And do the chapters under a timed setting. Once you are comfortable with the concepts, silly mistakes are the biggest challenge. And one tends to make silly mistakes a lot more under pressure.
Once you have finished a chapter and marked your answers, the most important thing is to go back and review your answers, and not just the ones you got wrong. Occasionally I found that even if I got the right answer, there was often a quicker way to do it. Example: For any cube with side length x, what is the inner diagonal? Well obviously it's easy to solve using pythagoras' theorem. But, you pick up useful things like the the "super pythagorean theorem", which says that for any cube with side length x, the inner 3D diagonal is always x√3. Anyway, point is, reviewing is important. It's not all about just getting it right, but being efficient about it. My strategy was that I'd 'star' any problem that seemed tricky while I solved it, or which I got wrong. And I'd go back and review it in detail. If it was a silly mistake, it matters less.
The verbal reasoning part had only two components that I felt I needed practice and some training:
I found the Magoosh Vocabulary Builder app to be super handy and, dare I say, fun. It gives you a simple, casual way to build your vocabulary while on the bus or lazing around. I found that some new words began popping up for me once I reached Intermediate level 6 onwards.
While doing practice questions, I found that I was most prone to error on the RC questions. There's no real magic solution here, just more practice.
One decision I made: no paper-based practice tests. Given that the computer test is section adaptive, the paper test really doesn't compare. I did 3 practice tests: two from ETS powerprep and one free from Manhattan Prep (The Manhattan 5 LB Book also gives you access to their super nice online portal).
Final tips:
Pace yourself. I took it easy the last 3 days before the test and made sure I was sleeping well and not stressed out.
Have a mental list of formulas etc you should know (Magoosh has one online). Probabilities, geometry, exponents, combinations, etc.
Identify and focus on your weaker areas. For me, my weakest area was prime numbers and divisibility. So I made sure I spent extra time on that.
Alright, that's it for now! If you have general questions, I'd be happy to answer them. Although I'm based in India at the moment so there might be a half-day delay owing to time differences.
Good luck!
Edit: Minor errors.
For written, as most posts here focussed on spoken.
Among many other things you've been advised here, is to read newspapers and novels daily, I'd say skip that in favour of aldaily. Far superior. Also if you pick up a shitty novel, you'll be stuck with it.
Read an essay everyday and write it down in your own words to the best of your recollection. Reuse phrases if you need to. Don't look at it again though. Most importantly, compare what you've written.
Also learn up this word list by Magoosh. When you're done with these, find a set on Quizlet and master it. Don't go through Norman Lewis, simply because you'll never finish it. You'll get bored.
I prepared for GRE this way.
To recap,
1 essay read and write daily from aldaily
Learn up the wordlist, one set a day (a set takes an hour approx), then keep revising.
Below are the links for magoosh apps that I used:
https://play.google.com/store/apps/details?id=com.magoosh.gre.quiz.vocabulary
https://play.google.com/store/apps/details?id=com.magoosh.flashcards.gre&hl=en_IN&gl=US
I used Gregmat's list for practice as well. It is paid content, and I will recommend you get it if you haven't. It's totallllly worth it.
While I already mentioned Membean, beyond that, it really depends on how much time you have to prepare. When I was in high school, I had a lot of Korean friends who were struggling with English, and I noticed that going through long lists of vocab was quite hard for them because it is difficult to memorize large quantities of random-seeming information without any context. That is one reason I like Membean - they try to use each word in several different ways with images and mnemonics to help you absorb them. The most popular GRE mobile apps on the other hand (like Magoosh) tend to just focus on rote memorization, which is more difficult and less sustainable.
At the GRE level, there are two other ways I can see to strengthen your grasp of English:
1) You can memorize roots of words, which is a great way to get an intuition for what an unfamiliar word means just by glancing at it. You'll be surprised by how effective this can be.
2) This is more time-consuming, but if you have a lot of time, you can try to read some books in English. They don't have to be classical literature or anything - stuff like Game of Thrones is fine as well. If this sounds compelling to you, check out /r/books and ask for recommendations. Whenever you find an unfamiliar word, take the time to pause and Google for its definition, and think about how the author is using it. This is a more low-stress way to pick up new words, and it tends to be more effective in the long run. Plus, it will strengthen your ability to parse and analyze the passages in the Verbal section.
Best of luck! Becoming fluent at the graduate level in a foreign language is really hard. It's a very impressive achievement to have.