Because hiking is a recreational experience, it's reasonable that hikers might expect it to be pleasant. On rare occasions, hikers can interfere with each others' enjoyment, or that of other users of the land, but they can minimise this interference by following a set of basic good manners. For example:
* When two groups of hikers meet on a steep trail, there may be some contention for use of the trail. To avoid bad feeling, a custom has developed in some areas in which the party moving uphill has the right-of-way. In other situations, the largest group will usually give way to the smaller.
* Being forced to hike much faster or slower than your natural pace can be annoying, and physically irksome to maintain. More seriously, walking in an unnatural way increases fatigue, may lead to exhaustion, and even cause injury. If a group separates themselves out between the fast and slow, the slow hikers may be left behind or get lost.
A common courtesy is to encourage the slowest hiker to hike at the front and for everyone to keep to that speed. Another custom is to have an experienced hiker bring up the rear, making sure that everyone in the group is safe and nobody lags behind.
* Hikers often enjoy a little quiet while taking in their surroundings. Loud noises, such as shouting or constant raised conversations, disrupt such enjoyment. Some hikers deliberately avoid abrupt and loud sounds, out of thoughtfulness towards other hikers. Keeping reasonably quiet will also increase the possibility of encountering wildlife.
* Hikers sometimes unwittingly trespass onto private property from public land or rights of way. This can alienate the property owners and result in the closure of hiking rights-of-way. To maximise available hiking territory for everyone, most hikers will either stay on public land, or obtain permission from land owners. Staying on marked hiking and walking trails avoids the possibility of innocent trespass.
* When different parties of hikers meet, it is considered common good manners to exchange some form of basic greeting, like a smile or a very casual wave. To pass another party without such acknowledgment is seen as rude.
* Take care not to allow tree branches to snap back in the face of hikers following you. Always allow enough space between yourself and the person behind to avoid the hazard. Similarly, if you are behind someone else, leave enough space for this. A stout smack in the face from a sprung branch can be painful at the least.
Most of this is common sense...treat other people as you would like to be treated and you won't have to think too much about manners and hiking etiquette.