The essence of Leadership is delegation of responsibilities. Know who you're going with and what they are good at or enjoy, then assign them a task or responsibility that conforms to that.
The first point in delegation is to define what are individual and group responsibilities. If everyone is going to be responsible for thier own food, clothing, and shelter your task gets much easier as all you need do there is give advice, guidance, and information, and perhaps an offer to review thier individual choices for comment and/or approval. Most camping trips fall into this category as most folks have thier own ideas about things such as food and clothing, your biggest responsibility there would be to insure everyone is making safe and sane choices and finding ways to gently and lovingly tell them that they are out of ther freaking minds if they haven't.
It gets a bit more difficult of you decide to break the trip up into group responsibilities, although there are some that can work well.
An easy example of this would be food and cooking. If you have someone who is good at cooking, delegate them as cook and menu planner, give them some advice and goals to meet (two breakfasts, three lunches and two suppers for five people that will weigh less than three pounds per person). Find out what kind of stove will be used and who will carry it, etc.
One other thing is to be aware of "implied tasks" that might need to be explained, especially to someone who is new to the activity, and this is where checklists come in very handy as they are a good way of outlining implied tasks without insulting the intelligence of the person who is being assigned.
For instance, if you assign someone to make soup, your checklist for them would include the ingredients, cooking pot, utensils needed, clean up supplies, and a box of bag to transport it all.
If you're unfamiliar with the task (somebody tells you that they are going to make Chicken Cordon Bleu on the campfire), you ask them to provide you with a checklist. That way they haved to think things out before they even get started. Its also a good way to assign small tasks to other people (Johnny will get the chicken, Tommy will get the cheese).