I always believe that trekking is all about exploring the new and enjoying the view while finding the best in you. You got to proceed through the entire exploration thing of yours in such a way that neither it should affect the fellow trekkers nor should ruin your trek in any way. And the best way of doing so is by learning about some of the most basic trekking etiquette.
Greet and Acknowledge
Learn to smile or to nod your head a bit when you meet someone, because none of the two cost you anything but gives a nice impression about you to the fellow trekkers and hikers. No one is going to scold or beat you if you don't but in the mountains, it is a simple friendly gesture that can brighten up the others' day.
No one is telling you to hug or make the other hikers your best buddies. But, a simple "Hi, Hello, Good morning, How was your trek?" can lighten up the mood of both you and the other trekker. Plus, learn to respect the religious sentiments and faith of others especially the locals.
Give the Uphill Trekker the Right of Way
Has anyone ever told you to give the uphill trekker the priority of continuing his/her uphill climb? If not, then know that it's a crucial trekking/hiking etiquette that you need to learn immediately. While on a trek, there are many trails that don't have enough room for two or more people to trek side by side. Therefore, the right thing to do in such situations is simply letting the uphill trekker continue his uphill trek, while the trekker going downhill should move aside making the narrow path clear.
However, if the upward-climbing trekker opts for a halt or motions you not to stop, you can happily keep going down your trail.
Don't Start Bragging About Everything
Bragging is probably the last thing any true hiker or trekker should do. From my own experience, I can tell that I've come across people (not trekkers, as trekkers don't do this) who continue to brag about their trekking equipment, the fine technology of their gears etc. What you need to understand here is that trekking is not about showing off the brand of your shoes, the price tag of your hiking pole, or the superior technological aspects of your watch. Trekking is not bragging about anything at all.
While you may be a gear-head, others may be more interested in simply enjoying their stay amidst nature and the mountains. Even asking about the miles one has covered for the day or how quickly you covered certain distances or how heavy is the backpack you're carrying compared to others, is a really cheap thing to do. Making queries about such things or judging others based on their mileage, backpack weight or gear qualities won't get you anywhere. Instead, why not have a general talk and share your experiences with others! Remember, taking pride in your achievements is not bad unless they come off as judging or bragging.
Do Not Leave Any Trace Behind
Just be honest and tell me how would you feel if you find plastics and litter all around on a camping ground you choose to pitch your tent on? Or how would you feel if you see wet tissues left here and there through the trail with stains of faeces on them? I know, it will make you sick and curse the trekkers or hikers who did those things. Then don't you think that you should not litter a place as it may cause the same irritation and discomfort to the other trekkers arriving after you?
Make it a point to leave no trace behind, whether it's your tissue or the wrapper of the snack bar you were eating. For bio-degradable waste, you can simply dispose of them by digging up a hole, putting them there and covering the hole properly with soil or rock. In order to dispose of non-biodegradable materials, such as plastic wraps or sanitary pads, carry them in a zip lock bag till you get to a nearby town and dispose of them properly there. When leaving in a trekker's hut or home-stay, make sure to leave the accommodation as it is. Please don't indulge in writing or engraving your name on the furniture or the wall. It's a simple etiquette that not only helps to keep the environment clean but also makes you a true traveller.
Don't Disturb Others While They Are Sleeping
I do admit that I take terrible pleasure in keeping my tent-mates awake with chitchats and horror stories during the night. But, wait, here I'm talking about my friends whom I camp with. When it comes to other fellow trekkers, it's important to not interrupt their sleep. Imagine, reaching the campsite during the night time when others are asleep in their tents or at least preparing to do so. In that case, flashing the bright headlamp of yours should be a strict no-no. Whatever you need to do, be quiet and less-bright about it.
Be it a night stroll around the campsite or a midnight photography attempt, make sure to switch on the red light setting of your headlamp. You may find the night worth wondering around or simply sitting outside and looking at the sky; but you need to respect the fact that for others, it's midnight and they need to sleep.
Remember, whether you're on a trek or hike or normal travelling, the ultimate purpose of your journey should be to witness nature and the surroundings at its best and unspoiled form. Hence, whether the other team is walking very slow or too fast should not be your concern. Trekking or hiking is no race. All of us trek or hike a trail in our own way. Hence, know your etiquette well, and don't give others a chance to complain.