Confidence is key. As with many things involving confidence, use of judicious preparation can be your friend. Not everyone starts out fully conversant and intimately familiar with a rule system like Athena springing from Zeus's brow. Equally those demanding intimate knowledge of a game system (especially a new one) from their GM violate Wheaton's Fifth Rule (unsafe for work link), to summarise - don't be a dick, quit your bitching and have some fun.
- Page Markers for the pages in your books that keep being referred to. If you're not a collector, these save you plenty of time leafing through books. If you are, you have a reference copy right?
- Cheatsheets for commonly used rules and references and fitting things like movement & combat basics on one side of A4 forces you to trim excess baggage. Making them look good helps, too much information can be distracting and difficult to use. Some are blessed with so many options that they have to do this for each character.
- 4th Edition D&D - Combat (kiznit), For Dummies
- OGL/3.xE - Cheat sheets (3.5E), Combat & Skills (3.5E),
- New World of Darkness
- Frequently Asked Questions don't have to be in web or electronic format. If the same questions keep coming up, it's worth writing the answers down. It saves time and it keeps things consistent if you can't always remember the difference which combat actions are move and which are minor.