Investing As A Young Man/Woman

I'm a young man. So essentially I'll be telling you my investment strategy. Just ride along.

1. Start early. Start now. I made my first investment in stocks at age 19 and I have not stopped investing actively ever since. Starting that early made my losses small in absolute value and my learning very great in comparison. The first 5 years I had nothing to show for my investing, well, except the knowledge I gained. I lost all my first investments in stocks. Everything. Even before the crash of 2008 came and removed all hope. The first company (shares) I bought was an insurance company and it was doing very well. I even got excellent dividends and felt very happy. The next one I bought with all the money I had was a bank and till today I don't have any shares certificate or any way to claim the shares I bought. It all just vapourised. They didn't send me a share certificate and when I went to the registrars to have things fixed I was just being referred from one place to another and section to another section till the bank got bought/merged with another bank and all hope again became lost. So my first five years of investing involved a lot of losses and unpleasant experiences. If I wasn't very young when I started, those losses could compound into serious family problems and maybe years of salary savings gone. As with all things, one is better at mastering a new skill (investment, in this case) starting at a young age.
2. Dollar Cost Averaging. In 2011, I set up a direct debit to monthly deduct money from my account (then, my salary account) into my investment account with ARM every last day of the  month. It helped me become comfortable with investing monthly and regularly. Now investing has become a habit for me. I am a lot more comfortable with putting away my extra income (money left after deduction for living expense and business running) into my investment accounts. It has helped me buy at every price point in the stock market over the last five years and I have a low average buy price. Despite the downturn in the stock market these periods, I have made gains because of this strategy. And on course to making further gains as stock always get to new highs, recovering from all previous downturn. 
3. Spending is never investing. You don't invest in a new car. You don't invest in a vacation. You don't invest in new smartphones. No matter what the adverts and marketers say, spending on items you are not planning to sell for gain is not an investment. And as a young man, delaying spending/gratification is key. There are endless stories of riches to rags; big boys who ended up as poor old men. Better if you get others to pay for your traveling/vacation and those things you want to enjoy. Or just hold on till later years to get them. In the end you will get them but you shouldn't sacrifice the time advantage of compounded interest/gains investing young gives you. You can never get back time lost in the investment world. But you can always buy (even a newer/better model) car, bigger vacation and better gizmos.
4. Avoid bad influence/friends. Peer pressure is real and strong. You can't overcome it you can only avoid it. So avoid bad influence.

All the best!