You do not need to use capital letters in Mirlyn.
An asterisk (*) or question mark (?) can be used to truncate search terms, i.e. to find words that have a common root. Use an asterisk for multiple letters (optim* will find optimal, optimum, optimization) and a question mark for single letters (wom?n will find both woman and women).
Use quotation marks to search for exact phrases ("occult fiction").
You can select a connector ("AND", "OR", or "NOT"), but usually you'll want to leave this as "AND" in order to get the most relevant results
Do not use punctuation; for example, women's studies should be womens studies.
If you leave a space, Mirlyn will automatically perform a search for the terms with "AND."
This tutorial gives some basic tips on performing keyword searches in Mirlyn, U of M's library catalog.