Customs regulations are the same for Guadeloupe as they are for France. There are no abnormal restrictions, though it's important to note that anything made from coral or turtle shell is illegal and will be confiscated if found in your bags.
All visitors to Guadeloupe must have a valid passport (or a valid national identity card if you’re an EU citizen). A round-trip or onward ticket is officially required of visitors. This may be checked at customs upon arrival, though it’s unlikely.
Immigration rules in Guadeloupe as the same as those for mainland France. Citizens of the USA, Canada, Australia and New Zealand can stay for up to 90 days without a visa. Citizens of the EU can stay indefinitely and can live and work here without any special documentation. If you need a visa for France, you'll need one for Guadeloupe as well, and should contact a French embassy sometime before you plan to travel.