Writing advice from C.S. Lewis
Yet another timely contribution from Letters of Note:
2. Always prefer the plain direct word to the long, vague one. Don't implement promises, but keep them.
3. Never use abstract nouns when concrete ones will do. If you mean "More people died" don't say "Mortality rose."
[...]
5. Don't use words too big for the subject. Don't say "infinitely" when you mean "very"; otherwise you'll have no word left when you want to talk about something really infinite.
Read the rest here.
My first instinct when writing is always to dress up everything in big words, but I think most people are more formal in their writing than in their speech. (I'm speaking here of Writing, not emails and text messages.) It has to be unlearned.
(For instance, "timely contribution"? It doesn't help that I would probably say that in conversation, too.)