Amount of money.
When investing I would recommend putting a decent amount of money into your investment. That way you will be making more money than just putting a few dollars in. Think of it this way, if you receive a 100% return but you have only invested 5 dollars, you have only made five dollars. But if you have invested 5,000, you have made 5,000 dollars.
Short term or long term.
Generally speaking, short term can be more risky than long term. While the payoff is quicker on this type of investment, it is also much more risky. The bigger the risk the bigger the reward.
Know when to withdraw your money.
Even if you have an investment that has been making you lots of money over the years, know when to get out. For the most part, all good things must come to an end. Just make sure you are not at the end when you figure that out.
Watch your investment.
The more you watch your investment and know about it, the better off you will be. That way you will not be guessing what you are doing, you will have some facts to back it up.