Many of you may know about George Washington's list of 110 Rules of Civility & Decent Behavior in Company and Conversation (if you don't, you can find it here). But how many of you knew that this extensive list includes some important lessons on investing?

OK, so there's really nothing about this list has to do with investing, but to have a little fun in celebration of Washington's birthday, I've twisted a few of the rules into important reminders about good investing.

Number 38: In visiting the Sick, do not Presently play the Physician if you be not Knowing therein.

Know what you know and know what you don't know. Do you need to have a doctor's level of expertise to buy a stock? Perhaps not, but buying a stock on a whim in an industry that you have no knowledge of is probably not going to end well.

Maybe you don't have to be a casino executive to invest in Las Vegas Sands (NYSE: LVS), but you better know that despite its name, most of the company's growth opportunities are overseas. You should also be familiar with important metrics like slot hold and what it means for the company that it was up across nearly all of its properties last quarter.

Similarly, you probably don't need an electrical engineering degree to buy SanDisk (Nasdaq: SNDK), but you'll need to be familiar such things as how the broader cycles in the memory industry work and how to figure out whether the lower margins last quarter mean imminent trouble for the company.

Number 49: Use no Reproachful Language against any one neither Curse nor Revile.

I thought I'd use this as a nicely worded reminder to folks on the Yahoo! Finance message boards (and elsewhere on the Internet). Investing can be a stressful endeavor, but there's no need to channel your middle-school bully when interacting with other investors.

Number 50: Be not hasty to believe flying Reports to the Disparagement of any.

Let's go ahead and extend this from just disparaging rumors to all rumors -- particularly buyout rumors. Look, a takeover can be great, particularly if the price is right, because you get a quick jump in the stock price.

However, the excitement over takeover rumors can also lure in speculators, jack up the stock price, and then slam those Johnny-come-latelies when a deal never materializes. And just how often do buyout rumors lead nowhere? Very often. Earlier this month, reported that Akamai (Nasdaq: AKAM) has been a rumored takeover target 21 times since 2005. For those without their calculators handy, that means Mr. Market is talking takeover for Akamai roughly every quarter.

Number 69: If two contend together take not the part of either unconstrained; and be not obstinate in your own Opinion, in Things indifferent be of the Major Side.

Very simply, if you endeavor to invest in individual stocks, you're going to be wrong sometimes (I've certainly had my share). As Washington's list reminds us here, you shouldn't be "obstinate in your own opinion," and for us that means being willing to admit that we're wrong and take action to prevent unnecessary losses.

Investment manager Whitney Tilson recently gave a very public display of how this is done as he closed out his short position in Netflix (Nasdaq: NFLX). After watching the stock soar and the company report strong results, Tilson decided that he'd botched his call and waved the white flag.

Number 90: Being Set at meat Scratch not neither Spit Cough or blow your Nose except there's a Necessity for it.

This has nothing to do with investing, but just don't do it. Seriously. It's gross.

Akamai Technologies is a Motley Fool Rule Breakers choice. Netflix is a Motley Fool Stock Advisor selection. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.