Take an online course, such as Magoosh, Kaptest, Princeton, Manhattan, etc. For Verbal section, try to learn as many vocabularies if you can.
Barron’s GRE 3500 Master Word List 1-5()
Barrons GRE Wordlist 4,759 words
GRE Word Lists
GRE Word List
If you have no time, learn these lists:
GRE High Frequency Words
The 357 Best GRE Vocabulary Words: Complete List
Top 101 High Frequency GRE Words
Top 52 GRE Vocabulary Words