Beware of liabilities disguised as assets (e.g. buying main property and preventing any other investment)

A massive expense taken away from your income every month is a tell-tale sign of a liability

Profession pays the bills. Your business is what will make you wealthy.

Use thorough analysis.

Focus on pricing. Buy only stock when its price is below its intrinsic value, i.e., its value as it relates to a company's propensity for growth.

Analyse the long-term development and business principles of the companies in which you're considering investing before buying any stock.

Protect yourself against serious losses by diversifying your investments.

Understand that you will not pull in extraordinary profits, but safe and steady revenues.

The first thing you should do before you invest isn't to look at a stock's history. That's important, sure, but what's more important is looking at the history of the stock market itself.

Then, look, for example, at the correlation between stock price and the company's earnings and dividends over the past ten years. Then consider the inflation rate, in order to see how much you'd really earn, all things considered.

Defensive investor's strategy: Safety is main focus. Invest in both high-grade bonds (e.g. AAA government debt securities) and common stocks. 50-50 or 75-25. For common stocks, invest in ~10 diverse, big, well-known companies with long histories of success.

Use "formula investing", a.k.a. "dollar-cost averaging". E.g.: always invest the same amount every month. Readjust your portfolio every 6 months.

Enterprising investor's strategy: more common stocks than the defensive investor's strategy. Take higher risks. But no matter how exciting or promising an investment opportunity seems, limit high risk stocks to a max. of 10% of your overall portfolio.

Never buy a stock immediately after a substantial rise or sell one after a substantial drop.