All visitors to Guyana will have to fill out a customs declaration form on arrival before going through the red or green lane. In general checks are thorough and penalties for making a false declaration are stiff, so be entirely transparent.
There are no unusual rules about what can be brought into Guyana or taken out.
Travelers from the USA, Canada, EU countries, Australia, New Zealand, Japan, the UK and most Caribbean countries do not need a visa; confirm with your nearest embassy or consulate. A 90-day stay is granted on arrival in Guyana with an onward ticket. If you do need a visa, file your application at least six weeks before you leave your home country. As well as a passport, carry an international yellow-fever vaccination certificate with you (although you probably won't be asked for this), and keep other immunizations up to date.