The only thing you have to do is to use these troublesome words in appropriate contexts.
Strategies: reading comprehension, repetition, exercise and ..:
I hope these help:
Active Reading Strategies, Mind Tools Reading Techniques...
Allusion vs. Illusion***
Allusion: an indirect reference to something.
There are many wonderful classical allusions in this story.
Illusion: a false impression
Despite Umbridge’s smiles, no one fell for the illusion.
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When you have vanity you are conceited: you are vain. “You’re so vain you probably think this song is about you.” This spelling can also mean “futile,” as in “All my love’s in vain” (fruitless). Note that when Ecclesiastes says that “all is vanity” it doesn’t mean that everything is conceited, but that everything is pointless.
A vane is a blade designed to move or be moved by gases or liquid, like a weathervane.
A vein is a slender thread of something, like blood in a body or gold in a mine. It can also be a line of thought, as in “After describing his dog’s habit of chewing on the sofa, Carlos went on in the same vein for several minutes.”
When the weather is warm and summery and you don’t feel like spending a lot of time reading that long report from the restructuring committee, just read the summary.
summary, summaries- WordWeb dictionary definition