Many learners of English may have trouble memorizing new words. They try one and a thousand of ways to learn the new words by heart. The commonest way is to recite the words from a vocabulary book or to keep word lists. But the best way, however, is to read a great deal, attend a lot of lectures and be alert to the formation of words. Here are some suggestions.
Read plenty of books. When you come across a new word, or a new meaning of an old word, see if you can infer it from its context (the words around it). If you cannot, lookit up in a dictionary or ask somebody and then repeat its meaning to yourself a couple of times. If you are really conscientious, write the word and its meaning in a personal vocabulary list with a sentence under it. Go over the list from time to time. Further, try to use the new word in writing or conversation a few times over the next few days.
Listen to good lectures and be alert to new words you hear or to new meanings of words you already know. Then treat them just as you do new words you read from books.
Learn and be alert to the formation of words: prefixes, suffixes, and roots. Knowing them enables you to make intelligent guesses about the meaning of words you meet next time. Check the etymology of a word in a good dictionary.
If you will follow these suggestions of mine, your vocabulary will undoubtedly be enlarged and your ability in other language skills improved.