Climbing trips are the easiest: all you have to do is drive out to the desert with ropes and food. Ski-hut trips are relatively simple, too. All the gear, shuttling, and logistics that go along with raft trips make them more challenging to organize. But they’re also the most fun.
Plan at least six months in advance to be sure you can obtain permits and property bookings. If the activity is technical, make sure everyone has comparable skills.
Keep it small at first and let it grow organically. Email an invite to a core group and tell them to reserve spots with a check. Then open it to a wider group with each subsequent trip.
Reserve the same week every year.
One person needs to manage the money—Google Spreadsheets is a good tool. Plan for $15 per person per day for food.
Have fun—bring instruments or costumes. And whiskey.