If you have to lead people on any sort of outdoor activity, from a family-and-friends trekking party to a full-scale expedition in search for meteorites fallen in Antarctica, you have to ask from yourself more than from others or face discontent.
Group leaders in any sort of environment requiring any level of physical, intellectual or mental straining from fellow participants, explorers or subordinates require more than just formal authority, especially if any sort of hazard or inconvenient develops or if survival is at stake. Leaders should never ask from others more than from themselves; if subordinates find out or reach the conclusion that their leader is someone very demanding with others but not so with his or her own affairs then the person in that position becomes automatically disqualified in a moral sense for the job and no rule, law or regulation will save him or her from inevitable ridicule. The group will not function properly again until its members are convinced of the contrary, either by making their leader change or changing their leader.
Even if there is a full-scale, stringent formal system to back up your authority, that will be no guarantee, especially in extreme situations in which there is no certainty of the future and hence, no certainty about the applicability of the rules that sustain you position. People may even expect you to lead in these circumstances, but will not be so keen to obey your commands. So, believing that you will be able to lead based on your formal authority as the company's boss, head of a family, military commander, chief scientist or just being the tallest or strongest is a delusion. In fact, if you just rely on that you will end up in a worse situation because formal authority will - as we just explained - make others assume that you should lead and be responsible for the group, but if you lack the skills necessary to exercise authority informally then they will not obey or hear your advice. People may even use your rank as an excuse to cover their own blunders; having formal authority is really a sword with two edges.
What a leader needs is trust; if people trust you then you are transformed in their minds from being a boss to the state of a true leader, and the best way to achieve such a goal is to lead by example, even with small or seemingly trivial things. For example, if during a stop someone takes a canteen out of the backpack in order to drink water, don't be the first to ask. Fist let others share it and save yourself for the last turn.Other little things that may help are: Getting up earlier than anybody else in your camp and being the last to enter the sleeping bag, always taking the seemingly smallest portion of food, cleaning your things and keeping them tidy. All these small habits will become evident to others and they will start emulating you; that's the beginning, and they will gain trust in you.
Never try to convince others by complaining about what they do; show them how to do those things correctly and then some. Make them believe that they can trust you with facts.