Basically, on a no-budget film you end up wearing a lot of hats. When you have fewer people shifting as much work as possible to pre-production and doing planning and contingency planning is what'll save your bacon.
I may have mentioned this upthread, but when we did what became "Stagecoach In the Sky"
for the 2009 48 Hour Film Project we did as much work as the contest rules would allow long before the actual contest: I secured a location 5 weeks in advance and toured it with my DP several weeks beforehand, taking a lot of photos and discussing with him the practicalities of shooting in the plane. The lighting gear we rented was based on this assessment. This planning made it possible for us to walk in on the shooting day and get right to it. It saved us HOURS of time during the shoot.
In other words: plan everything you can, then keep planning. It's never too much.