Reclining your seat is your right, but it might be unsettling for the person behind you, particularly if they're using a tray table or laptop.
Air travel involves conversations, but being too loud might disturb others. Use your indoor voice and watch the loudness while talking.
Playing games, viewing films, or listening to loud music might annoy surrounding people. Use headphones or lower the volume to prevent bothering others.
Note that airplane seats are not large, so don't invade your neighbor's space. Keep your arms, legs, and belongings in your area.
Traveling with kids or dogs requires discipline. Unruly kids or noisy dogs might bother other travelers.
Long trips might be difficult, but it doesn't excuse poor hygiene. In a small environment, body odor and fragrant food might be irritating.
Keeping your seat upright while flight attendants serve meals is polite. This allows you and your other passengers to eat comfortably.