It's up to you, of course. But here's what other people have found useful:
- GPS / aerial maps / driving directions: Some way to get to your destination
- Camera: Record proof of reaching the target or take group photos (besides taking pictures of cool stuff)
Also consider:
- Snacks
- Water
- Cell phone (in case of emergencies)
- Games
- Tripod for camera (group photos)
- Book or laptop, if you need something to keep you busy while you're waiting for other geohashers
- Picnic blanket
If you're trying for any kind of MNIMB Geohash:
- Lights (in case it's winter)
- First aid kit
- Compass
- Another truck if your location is a swamp. Don't say I never told you to.
