These are the things that are good to know:
1. Remember the names of the people you talk to about important things
for example staffmembers, or other players if they are causing problems
2. Remember the exact date/time
write [time to get the exact server time. This way we can find what was going on very easily.
3. Take screenshots
there's things that cannot be logged or described with words... if you feel like taking a screenshot, do it. It might also be good laughing material

4. If you die and believe you were PK'd, contact a staffmember
on 18th may we are implementing a system that logs certain ways of playerkilling, that can be done even in trammel rules. Just don't die until a staffmember investigates and takes notes on the matter.
5. Insure your items, bond your pets
You never know when you might get disconnected, or when the server might get disconnected... many unpleasant things can happen, so it is advised that you insure and bond your precious belongings.