Noticed a few people doing a few thing currently viewed as 'unethical' at NZ sport climbing crags this last rockcraft. Im a bit bored so will outline a fewn basic rules i have picked up from developers and climbers over the years.

1) Don't use any crag hardware (bolts, rings etc.) for a moving, weighted rope. i.e. do not top rope through two ring bolts at the the anchor. Do not lower off by rethreading the rope through the bolts. Doing this wears out the hardware which, more than likely, some poor climber has missed a meal to put up there! You also run the risk of any nicks in the bolt surface (very common) subtly shredding your rope, or worse, detaching and going in your rope, shredding it from the inside out. 

Alternatives: Clip a locking biner through each bolt (there should be two), take a sling and equalise the two, another locking biner clipped through that sling is equalised, redundant and wears out your gear rather than the climbing community's.

http://petzl.com/files/all/en/activities/sport/tech-tips-multi-pitch-climbing.pdf  has heaps of great, informative diagrams on anchors and dos and onts, know them all, :)

As seen in the link above, clip your safety (sling and locking biner girth hitched to your belay loop) to the bolt (double it up with a quickdraw to the other bolt if you want (you should, bolts fail way to often)) Untie, thread the rope through the bolts, pull it through till both ends touch the ground, put the two end into your belay device, attach a prussic to the rope for backup, and abseiil off. The rope doesnt move through the bolts and you get down safely. Everyone wins.

Sometimes its ok to lower off, especially if there is clippable hardware at the top, but remember to check the state of the clips, gobble gobble yum yum used to have its stainless clips worn halfway through. So far i have only seen two of these types of lower off in NZ, both in golden bay.

Those were the big two, here are some more personal ones, but pretty universal.

Don't ever step on a rope.

Clip quickdraws the right way up (straight gate up/ silver biner up) 

Dont leave tick marks on holds/ don't over-chalk. 

Don't shout 'beta' at a climber, information on how to climb a route, without knowing the person wants it, usually its just annoying. 

It only counts if you lead it with no tension on the rope till the anchors :) 

And last i saw the Hangdog Climbing Commandments, detailed in the left toilet, were:

Thou shalt possess at least one quickdraw.

Thou shalt not say take! 

Thou shalt take big whippers. 

 Feel free to discuss.