Outdoor lines land best when you are actually outdoors: at the campsite, on the trail or waiting for a fish to bite, when there is time to talk and nothing else to look at.
Know the activity before you joke about it. Climbers, anglers and hunters have their own vocabulary, and a line that gets the gear wrong will be corrected before it is laughed at.
Campfires are the best venue of all: everyone is relaxed, nobody is in a hurry and a groan carries well in the dark. Trailheads, climbing gyms, fishing piers and outdoor stores come close behind, along with dating profiles that are mostly photos of mountains.
Keep them good-natured. People who love the outdoors are usually happy to laugh at themselves (the mosquito bites, the one fish all weekend, the tent that took an hour), and a line that shares the joke works better than one that makes it.

