Let me tell you a secret: Usually people who use large words are just trying to impress people. The point of language is to make a point, not obfuscate one. It's far, far more important that you speak clearly than that you use big, fancy words whenever you can.

If your teachers are giving you bad grades for not using bad words, then they aren't good teachers. I don't know of any college professors who would do that.

The only thing I can think they mean is they don't want the word "big" used a kajillion times....? Like use things like "immense" instead?

If I'm barking up the wrong gatepost, just ignore me...everyone usually does ;)

Basically, you need to develop your own vocabulary as to set you out from the rest. You don't want to use the same basic words everyone else does, but you don't want to use words that very people know. Plus with using big words, chances ar you use them out of context.

Still, if you know all the words already, you could use a Thesaurus to remind yourself of the words. Be careful not to get caught up in any traps with some of the words having different connotations.

I agree with Joemarc. I have teachers that mark students down if they overuse words. For instance, they don't want to see so many words repeated...it gets annoying to read. So they want you to vary it up a bit...not necessarily use bigger words, but use more descriptive words that people know.

Like Joemarc pointed out, you only need to avoid using words like 'big' or 'a lot' in formal writing.