1.Only invest what you can afford to lose.
2.Never invest in something you dont understand.
You wont immediately understand everything, thats ok. Do some research.
3.Dont day trade unless you spend a minimum of 6 hours a day on the markets.
4. Be patient and buy it on sale.
The third point is rather related to trading, rather than to investment. One of the main rules of investing is portfolio diversification. Do not invest the whole portfolio in 1-2 assets.