There are lots of ways to increase your range of English words and spelling accuracy. You just need a dictionary and a notebook or even your smartphone! Here are some tips:
Create your own vocabulary notebook. Every time you read, listen to or watch something, write down the words you don’t know, then look them up in your dictionary and write down their meanings in your vocabulary notebook. Go back and look over your new words at least once a week. Try using your new words as much as you can when you speak and write in English. This will help you remember the vocabulary you have learned.
Choose a few words from this list and then write them down in your vocabulary notebook. If you are preparing for IELTS Academic, look at Avril Coxhead’s Academic word List and follow the same instructions.
Don’t forget that when you’re using new words, look at the different forms of the word, such as the noun and verb form. Learn how to use them correctly and practice using different forms in conversation and writing.
For example: I am contemplating (verb); the book is contemplative (adjective); Contemplation is important for study (noun).
Once you have a good foundation of words, you can progress to studying collocations and phrasal verbs to increase your range and expand how you use vocabulary in English conversation and writing.