As Hurricane Irma roars over the Florida Keys after causing destruction in the Caribbean, here is a guide to how you can help the people it affects.

First, some general guidelines: The Center for International Disaster Information, a part of the United States Agency for International Development, offers useful tips on giving in the wake of disasters. Sending money is almost always the most efficient way to help, it emphasizes.

For those who find themselves near damaged communities and want to assist in person, the National Voluntary Organizations Active in Disaster, an association of disaster relief organizations, encourages people not to “self-deploy.” Instead, willing volunteers in Puerto Rico, the U.S. Virgin Islands or Florida can register to be contacted by relief workers by signing up on the association’s website. The Red Cross is also helping to coordinate volunteers.

How to give

Think twice before you send any blankets, clothes or toys into a disaster area. Transporting, storing and sorting donated goods can divert resources away from more pressing work.

“I can’t tell you how many times I have been in disaster situations where I’ve seen, literally, just warehouses filled with stuff that people give, just sitting there,” said Britt Lake, the chief program officer for GlobalGiving, a crowdfunding organization that connects donors with local relief organizations.

GlobalGiving’s Irma Relief Fund is accepting donations here. It vets the local organizations it helps fund and is well-regarded by charity watchdogs. (GlobalGiving prioritizes local organizations over the long term, but often steers money toward larger entities like Save the Children or the International Medical Corps during the early days of disaster response.)