Here are some items that are guaranteed to make the trip more comfortable and eliminate some potential problems.
1. Toilet paper in an air tight zip loc bag. This provides REAL comfort, but can easily be forgotten!
2. Car keys and if possible, give a spare key to your fishing companion.
3. Several watertight lunch bags to save your, remote entry car keys, cell phone, wallet, snacks, etc. As if, anyone would fall in!
4. Two bottles water at a minimum. Freeze one (be sure to remove some water before freezing to prevent damage to bottle) and keep the other in the cooler until leaving the car starting toward the stream. Drink the cool bottle first, leaving the frozen bottle for later.
5. Compass if you are going to remote areas.
Techniques: