1. Understand the Business You’re Investing In
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2. Investment Is Not a Get-Rich-Quick Scheme
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I think these are the two most important points and all the rest are rather irrelevant. Starting with point two, many people see in the media and movies that people put one sum of money into an investment and get super rich from it - but that is extremely rare and not how most people find success. Success for the average person is a long road that requires commitment and understanding that they should keep adding funds through good times or bad. It takes most people decades of investing before they will be able to enjoy the fruits of their labor, but when it comes it is abundant enough to retire on. As for point one, 99% of people would do much better just investing in diversified ETF funds rather than trying to pick individual companies because unless you have the time to research them you will be wasting money.
I highly agree but this should come with proper financial management, as the earlier reply stated. Without proper financial management, all the effort, money, and time will be in vain because it is more likely that an overexpenditure will happen. And that overexpenditure will likely kill the investment. At the beginning, overexpenditure may not be a problem because there are still funds that will fill up on the useless extra spending, but as time goes on, this useless extra spending will have weight and may give a heavy blow to the cashflow. So as much as possible, financial management should be applied even before an investment is made. This way, all things will go smoothly.