At the same time, there are literally hundreds of thousands of individuals who buy and sell corporate securities on one of the regulated stock exchanges or the NASDAQ regularly and are successful. A profitable outcome is not the result of luck, but the application of a few simple principles derived from the experiences of millions of investors over countless stock market cycles.

However, it might be best to not become too much of a market "expert". Some of the most famous and successful investors of all time, such as Peter Lynch, the famed manager of the huge Fidelity Magellan fund. He suggested that looking for clues in normal life is a great way to find opportunities. Lynch used to closely follow the shopping habits of his wife to see what brands people were buying. He believed that most people working professionally on the NYSE lived in a bubble.
By knowing how much capital you will need and the future point in time when you will need it, you can calculate how much you should invest and what kind of return on your investment will be needed to produce the desired result. To estimate how much capital you are likely to need for retirement or future college expenses, use one of the free financial calculators available over the Internet.

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.
It’s best if you can automate your actual stock investments. Robo-advisors can do this for you, or if you must, you can manually buy stocks every time you receive a paycheck and have money in your savings or brokerage account. The important point is that you make regular investments so that you aren’t tempted to time the market. Regularly investing the same amount is a form of dollar cost averaging, and it helps reduce risk in your stock investments.
Buy in thirds: Like dollar-cost averaging, “buying in thirds” helps you avoid the morale-crushing experience of bumpy results right out of the gate. Divide the amount you want to invest by three and then, as the name implies, pick three separate points to buy shares. These can be at regular intervals (e.g., monthly or quarterly) or based on performance or company events. For example, you might buy shares before a product is released and put the next third of your money into play if it’s a hit — or divert the remaining money elsewhere if it’s not.