Dumping things I've learned while using the OWL tool Protege. Most searches provide nothing for it and most tutorials are by foreigners who do not speak English well. I'm keeping it pretty clear and concise here. Folders organize things.
Ctrl + Space is the most important keyboard shortcut to know. You can use it just about anywhere (and in some places it is absolutely necessary). It's used when you're writing class expressions, finding instances to link, and changing an IRI base. Don't forget it. Watch some tutorial videos and you'll see where it's used.