I'm not talking about polishing school where you learn to become a lady with manners. I threw that out the window a long time ago. I'm talking about etiquette on the bike - on both the trail and on the road. Most of us know the general rules, but I often can't help but think that there are riders who simply don't know the rules(and then there is the group who simply doesn't care). I get annoyed and frustrated when I don't feel like myself or other riders are being respected, so here are a few pointers so you're not "that guy." 

As cyclists, if one guy screws up, cyclists are guilty by association.  Let's make a good name for us on the trails and roads.

On the trail:

• Always yield to the uphill rider.  In other words, don't go bombing down a trail at mach 5 and run the person riding up in the opposite direction off the trail.  I know we love bombing down singletrack, but not at the expense of others.
• Don't litter!  Pick up your trash, dummy!
• Stay on the trail. This seems like a no brainer, but by going off the trail, even a little bit, the singletrack is no longer so single.
• If you are going to stop, at least be aware of your surroundings.  Try to stop at a wider section of trail so you don't cause a traffic jam.
• Don't be a butt-head.  I.E.  Don't try to race people because they look fast.  Chances are, you'll make them mad and look like an idiot in the process... especially if you try to get in front of them just to get in front of them, slow down, and then end up in the way.
• Don't modify the trail because it's too hard.  That means, don't move that rock out of the way because it trips you up.
• If you see a horse, slow down and say something.  If you don't say something, the horse won't know what the heck you are and probably get spooked.  Give the equestrian time to move over and be patient.  Ask the equestrian how they'd like to you to proceed. I know this is hard sometimes, especially when they take forever and you're like, "AHHH MOVE!!!" 
• Give hikers the right of way too.  In fact, slow down...especially if they have dogs.
• Say hi to people!  It doesn't hurt to be friendly, right?
• Ride in control... you wouldn't like it if someone came right at you screaming and out of control.  Has that happened to me?  Yes, and I promptly moved out of their way.
• If you are walking a technical section and someone is riding behind you, don't walk in the line the rider would take.  This happens a lot in races.
• WEAR A HELMET!

On the road

• Pass other cyclists on the left
• This one is debatable... you're supposed to call out "on your left" to pedestrians.  In my experience, they usually freak out and jump to the left.  I usually just say, "Hi!  Excuse me!"  and watch how they proceed.  Head on collisions with people on foot is never fun for either party involved... or the small rodent like dog dressed in the sweater.
• Don't sit on someone's wheel.  You know who you are.  You see someone up ahead, and you get right behind them and draft off of them without saying a word.  This will really annoy the person you are behind and worse, it can be dangerous because they don't know your back there... OR they could brake check you.  Do your own work.  If you are coming up on someone, wave as you pass, or say hi.  Don't sit behind me and then "attack."
• Which brings me to DON'T BE A BUTT-HEAD.  Don't pass me, going .2 mph faster, get 10 ft in front of me and slow down... and then when I have to pass you again,  try to race me.  I'm not interested.  I don't care if you pass me, but please don't chase me down only to go slow... and then speed up greatly after I pass you again.  Please??
• Try to be nice to cars.  I know they suck sometimes, but it makes all of us look bad if you're waving the bird and screaming at the car who cut you off.  It's frustrating, but the car wins and the last thing we want is a bunch of motorists driving around with a chip on their shoulder about cyclists.  We want respect, but so do they.
• Try not to blatantly blow through red lights and stop signs.  At least yield. ;)
• Oh, wear a FREAKING helmet!
• Don't litter
• Don't take up the whole road.  I know we like to ride next to our friends on rides, but if you're taking up the whole lane... that's not cool.  (and another thing to annoy motorists).  This can also put the motorist in danger trying to pass you across a double yellow.  Share the road also means cyclists sharing the road with cars.  
• Be friendly.  I hate it when people think they are too cool to wave at you because um... you're NOT.

Think of something I left out?  Feel free to add it.  Think I'm being irrational?  Come spend a warm day on a bike in Boulder county when you encounter 100s of cyclists in one day and you'll understand.