As 2004 winds to a close, I thought it would be appropriate to review some of the articles I've written and share some lessons learned -- both good and bad -- with the Foolish community.

I have written about 60 articles since I began contributing to the Fool in May. With that many pieces, it's unlikely I could be correct every time. In every article, though, I tried to share the process that led me to my conclusion.

I'll highlight some of my highs and lows.

Where I went wrong
The worst call I made this year has to be a negative article I wrote July 15 on Qlogic (NASDAQ:QLGC). The company was down 50% for the year, as was competitor Emulex (NYSE:ELX). I felt that the drop in price was the market's way of communicating a real problem with the host bus adapter (HBA) market, a subset of the data storage industry. Qlogic is best-known for HBAs. Since that article the stock is up 34%, thanks to a better outlook for the storage industry. I was clear that I felt it would take an uncommon understanding of HBAs to know when to buy the stock. While the call was bad, I've always believed in avoiding stocks I don't understand. Going forward, I'll also avoid writing negative articles about stocks I don't understand.

Another stinker was a positive article I wrote June 4 on Idexx Labs (NASDAQ:IDXX). My premise was that it had a more predictable revenue stream thanks to a product line that does not swing for the fences. That predictability did not help the stock, which declined in concert with the biotech sector during the summer. It's down 20% since the story was published.

On June 17, I made a wrong call about Gemstar TV Guide (NASDAQ:GMST). The stock is up 31% since the story was published. The thrust of my negative article was a lack of visibility of demand for the magazine, the onscreen guide, and the website. I still don't see the demand, but the market does. A reader pointed out to me that I have access to the channel and didn't even know it. I doubt I'm the only one, but I didn't have as much company as I thought.

I also made some good calls about stocks to avoid.

Where I went right
I wrote negatively about Pfizer (NYSE:PFE) twice. My first article on Pfizer ran May 17, with the stock at $35.10. It has dropped 25% since then. The logic of that article was very simple: I questioned whether Pfizer's pipeline could add sufficient growth to a $52 billion top line to justify the stock price. I had no clue that the Celebrex problems would soon develop, but the stock dropped about 20% between the date of the that first article and the day the Celebrex news broke. After I wrote that first story, I got some very nasty email telling me how wrong and dumb I was. I may be dumb, but what's especially interesting is that the emails revealed an emotional attachment to the stock. Emotion can get in the way of all sorts of investment decisions.

I could write almost the same paragraph about American International Group (NYSE:AIG). I wrote a negative article about it on June 7, and the stock has dropped 11% since then. Two ideas were behind this article. First was the Spitzer visibility (New York State Attorney General Eliot Spitzer's investigation of the company) and the perception that insurance isn't too clean a business. My other idea -- and this pertains to an area of analysis the Fool as a whole tends not to endorse -- was that based on where we were in the stock market cycle, companies larger than $100 billion in market cap were likely to lag the market. In fact, of the 17 U.S. companies larger than $100 billion, 11 of them are trailing their respective sectors. Mega-cap companies usually outperform toward the end of a bull market, as demonstrated in 1998 and 1999.

Some of the stocks I liked have gone up considerably.

On June 9 I wrote about a small steel company named Quanex (NYSE:NX). I thought the stock might do well considering increasing demand for cars in China. The company doesn't have massive exposure to China, but the stock is still up 50%. The fundamental story of what will drive the company has not changed, but the P/E has expanded from 11 in June to 20 today. The stock may go a lot higher from here, but in my opinion buyers today are taking more downside exposure, given the higher price.

Mine Safety (NYSE:MSA) was a name that caught my eye crawling across the bottom of the screen on Bloomberg TV. I didn't realize it was one of Tom Gardner's Hidden Gems. Despite a couple of small valuation warts, like the fact that the stock was up 100% in the 12 months prior to my article and that it traded, back then, at 3.5 times sales, I felt the stock would do well, considering the obvious demand for the company's products. That demand still exists. Despite the 73% run since June 24, I think there is more room to grow, but it would be unrealistic to expect the same type of price appreciation. Earnings growth is expected to slow to 16% next year from 48% this year.

One last stock I'll mention is Taser International (NASDAQ:TASR). I wrote a positive story about it on June 23, citing again an obvious demand for stun guns. The stock is up 73%. The business was then and is now easy to understand, and Taser is likely to sell a lot more stun guns. The stock is, however, a hot potato. Very hot, on both ends. The next 20% movement in the price could easily be down. Long-term, though, product demand will obviously be the most important catalyst driving the stock.

The broader horizon
What I have enjoyed the most about writing for The Motley Fool has been the chance to share the process I use to put together a portfolio, and how to use different types of tools to try to get the same return with less volatility.

One way to smooth out volatility is by owning foreign stocks. In 2004 I wrote 12 articles about international investing. I believe foreign exposure will become more and more important in the next few years. Foreign stocks are generally cheaper with respect to their underlying businesses, and often come with higher dividends. And there are compelling arguments for investment capital to flow from the U.S. to other countries, including: weakness in the dollar, demand for commodities from countries such as Australia and Canada, money flowing into Chinese trade partners, and the potential for the Euro to share the role of world reserve currency with the U.S. dollar.

I've also sorted through new investment products, trying to sniff out the useful from the useless. There are going to be a lot of new ETFs and closed-end funds coming out that will try to capture certain areas of capital markets. It will be very worthwhile for all of us to learn about these products as they emerge, because some of them will make excellent and innovative investments.

To close, I will add that what I have tried to provide this year is a simple way to start the process of choosing what to buy for your account. The concept of supply and demand has played into almost every article I have ever written. If I can't understand how demand will drive the business, I don't even try to pick apart the numbers. I may have missed some upside opportunity because of that, but, on the whole, that lesson has served me so well that I hope I never unlearn it.

Investing can be as simple or as complex as you want to make it. I try to make it as simple as I can. Sometimes that works, sometimes it doesn't, but the only way to improve is to look back and learn.

Fool contributor Roger Nusbaum is an investment manager and wildland firefighter in Prescott, Ariz. At press time, neither he nor his clients owned any of the stocks mentioned.