During the initial planning phase, visit all roads and ramps along the route by vehicle. Inventory each site - type of ramp, disabled access, facilities available, etc. In an unpopulated area determine if adding a remote boat ramp to a map will be beneficial to a paddler. For example, if someone is looking for help in an emergency, will they be likely to find it?
Visit the trail during different seasons, different tidal levels, and after periods of low or high water. You may discover a campsite that floods during a storm surge or a site that is not accessible during low tide. Ask local people about the history of prevailing and extreme conditions on the waterway.
Examine topographical maps and aerial images of the waterway or coastline to identify sites with enough elevation and land cover for camping. Aerial photos are a good way to check for possible road access to a potential campsite; a feature that should be avoided if possible to reduce user conflict. Consider regional environmental concerns when choosing campsite locations, i.e., are elevated sites with breezes helpful for finding relief from summer insects?
Early in the planning stage, visit each potential campsite by boat. A powerboat can be used to do the initial survey, but be sure to paddle the route and stay at potential campsites as well. This provides a wealth of detailed information that can't be ascertained by powerboat alone and is essential to making a successful trail.
Collect GPS points for important channel markers, points of interest, campsites, confusing navigation points, etc. Take photos of navigation aids to help identify location of campsites, river channels, etc., on your map.
Paddle the entire route to verify GPS data and to determine where markers should be placed to clarify routes and identify campsites. Plan route to minimize the number of markers needed. This will provide initial and long-term savings and preserve the wilderness experience of the area.
At the onset of your project contact any land managers from public agencies or private landowners who may be affected by the development of a new trail near their property.