One year ago, I started to publicly announce the stocks I was considering adding to my Roth IRA on a monthly basis. The results so far haven't been bad, with the overall portfolio returning 7.4%. But that return is trailing the S&P 500 by 1.8 percentage points over the same time frame, and my lump sum growth and retirement portfolios have fared much better.

The No. 1 lesson I've gleaned from this relative underperformance is the importance of sticking with what I know and not being afraid to buy the same company more than once if I believe in it. Too often, I've ventured into stocks that I didn't fully understand or have a firm, long-term conviction in.

In that vein, all stocks I'm considering are ones that I already own, that I believe in owning for the coming decade, and that I believe are trading for fair prices. In today's article, I'll give you the big picture behind these four stocks; when I pick one to buy on Friday, I'll offer up a more in-depth view of my reasoning.

Baidu (Nasdaq: BIDU)
Two months ago, I bought this Chinese Internet search giant because I believed it would continue to benefit from being the webpage of choice for the growing legions of Chinese Web users. To support my case, I dug up some numbers on the story playing out on the other side of the globe:

  • In 2006, only 10% of Chinese residents used the Internet. Just four years later, that number had more than tripled to 35%. But that leaves 65% of the Chinese population yet to come online.
  • The Asian continent alone has 56% of the world population, but only 26% of those people were using the Internet by the end of 2011.
  • The total number of Internet users China added between 2005 and 2010 was greater than the entire population of the United States.

The stock is trading today at almost the same price it was back then. This is partly because some are worried that Qihoo 360 (NYSE: QIHU) is gaining market share in search.  But as fellow Fool Rick Munarriz points out, these price fluctuations just don't make sense. Even if Baidu is losing share, it's entirely possible that the overall market is growing so much that the overall impact isn't as bad as bears would have you believe.

Intuitive Surgical (Nasdaq: ISRG)
It was just one month ago that I added Intuitive Surgical to my Roth IRA, but I've been holding it in other accounts for much longer. The company makes the daVinci Robotic Surgery System, which is used to perform minimally invasive surgeries.

In the past, these surgeries have focused on prostatectomies and hysterectomies. But as doctors continue to experiment with the system, there are chances for the daVinci's use in a myriad of other fields and operations, including urology, lobectomies, and head and neck procedures.

Last quarter, 58% of the company's revenue came from recurring sources, which means Intuitive is more than just a system sales organization; it's also a service and parts company. That's an important distinction to gauge the company's long-term profitability.

The market is currently worried about a slowdown in procedures, particularly in Europe. But I think the current prices offer an opportunity for long-term investors.

Johnson & Johnson (NYSE: JNJ)
I'll admit it, this medical conglomerate isn't nearly as exciting as my other four candidates from a growth perspective. Rather, it's a well-entrenched company that is able to pay out steady dividends and is trading at what I consider to be a fair price. That's why I added it to my retirement portfolio over a year ago.

Currently, the company is yielding a fat 3.5% dividend for investors while only using up 50% of free cash flow to pay that dividend. Add in there the fact that Johnson & Johnson has raised its dividend for 50 consecutive years and grown it by an average of 8.7% over the past five, and it's easy to look past the company's recent missteps and focus on today's bargain offer.

Google (Nasdaq: GOOG)
Finally, we have the most visited website (and advertising platform specialist) in the world. On three different occasions I've bought into Google, and I see no good reason to stop considering the company's stock.

While some have complained about the company's impending stock split and the way Larry Page and Sergey Brin have made it almost impossible to lose their majority stake in the company, I'm just fine with it. In fact, the visionary leadership these co-founders provide is one reason I like the company so much: They have an ultra-long time horizon when thinking about the company.

Over the first half of 2012, the company has grown revenue by 23% and free cash flow by 34%, all while making sure it is investing for the future. Trading at just 17 times free cash flow, I think this solid company is a steal.

Tune in this Friday to see which of these four candidates ends up being my choice. In the interim, if you want to get the full scoop on Baidu, our very own Andrew Tonner has prepared a special premium report on this Chinese search giant. Access to the report also gets you exclusive ongoing coverage from our top technology analyst. Get your copy of the report today!