It's always a good idea to read the rules fully. They're posted on the website of the convention most of the time, otherwise request the organisation to mail you a copy of them. This will keep you out of trouble and allow you to plan your day a lot better. You now know what you can and can't do after all!
Please be aware that these rules exist for your safety in the first place. Also, the convention itself may be held liable for the things their visitors do. You wouldn't want to be responsible for a convention not held anymore, would you? It may sound a bit severe, but a lot off stuff happens at a convention that shouldn't. There are people harassing others or trying to deal drugs. It's not only against the rules, but also against the law. Also, a lot of cosplayers want to bring weapons for their cosplay. The convention staff often has a hard time trying to explain they can't. The reason for this is quite simple: conventions are crowded places, you could hurt others without knowing it. Next to that, some items are not allowed because of dutch law. Stuff like metal daggers and guns. Some events do allow it, but check the rules before you bring them.
Dealing with problems and people
Sometimes things go wrong. You as a visitor shouldn't have to deal with it, but when you do, be sure to tell someone representing the organisation. If you catch someone dealing drugs or stealing, harassment, stalking or other mayhem, walk up to a steward and report this person. The staff will handle it from there discretely. You can help them make the convention a safer place. Same thing goes for bootlegs in a Dealer Room. Walk up to a steward, gopher or staff member and report it. They'll handle it from there on.
Use your head and common sense, read the rules and you'll be allright!