What's the best way to secure outdoor carpet to a wooden deck?

There are very small carpet nails available at any hardware store. They have a small head (larger than a finish nail) and very sharp points so be carefull handling them. You do not want to glue down the carpet unless you know for sure that you will never want to remove it in the future as the bond is very strong

Staples, Nails, anything but glue! Someday you will want to remove i and the glue will never let go.

=\

screw it to a battern all way round.

in boat catalogues they make plastic "snaps" to hold carpets down. You screw one part on the deck and the other snap part on the rug. it keeps it down but also allows you to periodically and easily take it up to inspect, reseal, etc. They ar very easy to install.

staple gun

grommets or washers and screws!