Businesses you don't understand -- Here's a great rule of thumb that works for beginners and expert investors alike. If you can't clearly explain what a company does and how it makes money in a sentence or two, don't invest in it. There are literally thousands of publicly traded companies to choose from, and you should be able to find plenty of opportunities in easy-to-understand businesses.
Over the long run, value stocks outperform growth, so look for stocks trading at relatively cheap valuations based on price-to-earnings ratio (P/E), price-to-sales ratio (P/S), and price-to-free-cash-flow ratio (P/FCF). It is vital not to chase opportunities, but rather wait for them because patience always pays. Solid fundamentals and a large moat (barrier to entry) are also vital for long-term sustained success. Also, use technical analysis and charting to better help pinpoint both the entry and exit points for the stock under consideration—both for a target profit area and a stop loss.
The OTC Markets Group (POTCQX, OTCQB, OTC Pink): Formerly known as The Pink Sheets, these markets are considered very risky for penny stock investors. Since they have such a low standard to get started, and almost non-existent fees, just about any company can be publicly traded on them. By avoiding penny stocks trading on these markets, you can reduce the vast majority of downside risks of investing in low-priced shares.
This education really ought to include one of the daily papers that covers the movements on the stock exchange (information here) in detail, such as the Financial Times or Wall Street Journal. Remember, the investment bankers that you are competing against have Bloomberg terminals and Reuters subscriptions, while everyone else is watching CNN and MSNBC. Since everyone is reading the same things on the same days, these might not be the best places to pick up your share market tips...

The least demanding way to invest in the stock market is to invest through a fund. There are two types of funds. First is the actively managed mutual funds which have higher fees—92% of these funds fail to beat the underlying index over any three-year period. The second type is the index tracking fund, which typically has lower costs and is more effective in matching the growth of the stock market. This means they are growing in popularity because of the higher return on investment you receive. You should also use the most tax efficient way to invest: using your Investment Retirement Account (IRA) first. It’s best to invest in a low-cost, index-tracking fund through your tax-free IRA.

You’ll come across an overwhelming amount of information as you screen potential business partners. But it’s easier to home in on the right stuff when wearing a “business buyer” hat. You want to know how this company operates, its place in the overall industry, its competitors, its long-term prospects and whether it brings something new to the portfolio of businesses you already own.