If you are planning a hike on a walkway, such as the Hudson River Greenway, you may be able to lead the hike after only walking the route once. Check for detours and dangerous conditions, note the location of restrooms and dropout points, decide where to stop for lunch, and you should be ready to lead.
If you are developing your own route, it may take three scouting walks before you are able to comfortably lead a hike. The first time to establish the route, the second time to make minor adjustments and the third time to know every turn.
Restrooms are extremely important on a hike. Pick a meeting spot which has a nearby public restroom and try to plan a restroom stop about every hour and a half. Most playgrounds have public restrooms, however, note that they often close at 4pm. Malls and transportation hubs like the Staten Island Ferry Terminal all have restrooms that are available for use. If you have not walked the route in a while, be sure to check that restrooms will be open.
Plan for dropout points along the route with subway and bus transportation nearby.