The Rules

This is more for the roadies amongst us, but some also carry over to MTB:

http://www.velominati.com/the-rules/

This is great info. I have to admit I have done some of the don'ts on the rules list, like wearing spandex shorts while mountain biking. I just like the way they fit.

Just don't be a "Fred" .
I could be considered a "Fred " by some because i use a eyeglasses mounted mirror and I wear the road kit even though I weight 175-180 lbs.

Wikipedia definition of Fred

From Wikipedia:

Fred is a derisive term used by "serious" road cyclists to describe other cyclists who do not conform to serious road cyclists' norms with regard to dress and equipment, and appear amateurish to them. The term is generally reserved for men, while the female Fred is sometimes called a Doris.
The exact qualities that define one as a "Fred" vary widely among regions and cyclists. The earliest two definitions used for the term are contradictory.
In the UK, an early usage of the word is the more common—used by 'serious' roadies (cyclists who ride racing bicycles, and may themselves participate in competitive events) to refer to (stereotypically) bearded, sandal-wearing, cyclists without any high-tech gear.[citation needed] These Freds are not generally total novice cyclists, and often ride fairly frequently. This usage still survives in the US. David Bernstein, presenter of The FredCast says the term is "used by 'serious' roadies to disparage utility cyclists and touring riders, especially after these totally unfashionable 'freds' drop the 'serious' roadies on hills because the 'serious' guys were really posers."
More recently, particularly in the US, a Fred is more often somebody with higher quality and more expensive cycling equipment than his or her talent and commitment would warrant. For example, a stereotypical Fred by this definition would be an individual with little cycling experience who watches the highlights of a few Tour de France stages, then goes to a bike store and purchases a Trek carbon fiber Madone in Team Discovery colors, along with Team Discovery shorts and jersey. Thus outfitted with equipment virtually identical to that which Lance Armstrong used, far more expensive than that used by many high-standard racing cyclists, and more costly than many automobiles, the "Fred" then uses his bicycle merely to ride on a cycling path at 15 mph (24 km/h), something which even the most casual untrained cyclist can manage on an inexpensive hybrid bicycle. Some use "Fred" in a somewhat similar matter, but more synonymous with a roadie poseur. However, a Fred isn't necessarily someone who intentionally tries to put forth an image of being better or more knowledgeable than they are. Rather, a Fred is an inexperienced or unskilled cyclist who gets some top high-end or copy-cat racing gear for any reason. Unlike most poseurs, a Fred may still ride lacking some fundamental piece of competitive roadie equipment or style.
A third use of the term exists. In this usage, a "Fred" is a cyclist who has a ton of cycling gear, especially of the utilitarian "uncool" kind, like mirrors, powerful lights, fenders, bells/horns, heavy leather seats, racks, reflective gear, bags, baskets, etc. The gear and bike may be put together by kludgey homemade solutions, like duct-taped flashlights to the handlebar.[1] This type of Fred is a bike geek who likes/needs lots of gear (even if it is modified stuff not intended for bikes). Sacrificing some, or ignoring completely, concerns of speed or traditional roadie/sport cyclist style, these type of Freds are more concerned with practical concerns like comfort, safety, versatility, maintenance, being able to quickly transition to time and culture on/off the bicycle, etc. These cyclists may be well aware of their fredness, once they are aware of the concept, and often embrace it wholeheartedly

im surprised people actually care what im doing or wearing when i ride. let someone in tight pants tell me in person, they're not going to be sitting on that bike for long.

I'm a "Fred" as I, too, always ride the road with a eyeglasses mounted mirror and always ride any bike in my tight black shorts. IMHO, there is nothing better for mt. bike riding, since you're constantly moving around in the cockpit and saddle. I tried to be cool and bought a pair of true mt. biking shorts....fist big boulder roll, I went right over the bars because the baggy crotch got caught on the nose of the saddle. I gave them away and now only ride with tighties these days regardless of what bike I'm on.

I do love blowing by people who are on $5k bikes as I pass them on my 6 yo bike that I paid $1400 for! (Granted I have upgraded parts as they wore! But I do have 10k plus on it by now).

Doris checking in LOL.

Whatever...I'm out there, trying my best to keep fit, don't really care. I could fool you and look the part of real road biker, but all hope is lost when you see my basket pedals and converse all-star sneakers Ah well...will never be clipped in, have some innate fear of that, so will be a life-long Doris.