If you're investing in stocks to achieve financial security, following these 11 simple tips could help you avoid mistakes and build a bigger nest egg.SEE ALSO:CEO departures can wipe out billions from a company's value ' here are the Wall Street banks most at riskSEE ALSO:7 ways to save more and invest better, according to the expertsSEE ALSO:Millennials are making what could be one of the costliest investing mistakes in history1. Buy and hold, and hold, and holdThere's no secret sauce to stock market success, but perhaps, the best (and arguably, hardest to follow!) advice is to buy shares in great companies and hold them for decades.Sticking with stocks through bear markets can be hard, but historically, patience has outperformed short-term trading. Why' Because it's hard to know when it's safe to buy shares after selling them, and that can lead to missing out on some of the stock market's best performing days. For example, an investor who stayed the course through thick and thin earned a 339% return between Jan. 1, 1997 and Dec. 31, 2016; however, if they missed the 30 best performing days during that period, they'd have lost money, according toJP Morgan Asset Management.2. Keep some cash handyIf you're one of the millions of Americans without an emergency fund, you could be making a big mistake. The last thing you want to do is tap your stock portfolio for money during tough times. If you do, you could wind up selling shares when you should be buying them.Similarly, it can pay-off to have a little cash handy in your investment account. Holding cash won't earn you much of a return, but it can allow you to take advantage of the stock market's inevitable drops. Since 1950, there have been 36 periods when theS&P 500has fallen by over 10% and investing during those corrections improved the odds of investment success. The ability to profit from bear markets is one reason why some of the most successful investors of all time, including Warren Buffett, always keep some cash in their portfolio3. Dive into dividend stocksOne of the easiest ways to give your stock market returns a boost is investing in dividend paying stocks and then, using your dividend payments to buy more shares. According to Schroders, reinvesting dividends nearly doubles the return of the MSCI World Index to 640% from 323% since 1993. Because reinvesting dividends can help investors benefit from compoundinganddollar-cost averaging, make sure dividends are reinvested from day one.See the rest of the story at Business Insider Click here to read full news..