Here's a lesson I wished I learned earlier in life: As soon as you start making money, you should start a 401(k) or a retirement account.For the first few years of my working career, I was relatively inactive on the 401(k)-front. That changed around 2005 when I woke up and aggressively became involved with how my money was allocated. My neurotic nature carries over to my financial self, making me extremely cautious about my money and investments. But, like most people, I want my retirement money to grow, and I realize investment diversification is the key. (Click here: Free Friends to see my inaugural "Common Cents" column on MainStreet). Choose The Right Nest for Your Egg These days I have a significant amount of money in a money market fund, which might not be the best move, according Stuart Ritter, a certified financial planner for T. Rowe Price. "Having 30% in money markets is appropriate if you're 95 years old," says Ritter. I'm considerably younger than that. So I didn't have the heart to tell him I have nearly double in a money market fund with one retirement account, at an age where I'm expected to be a lot more risky. And, this is not due to headline news because despite checking on my account nearly everyday, I don't move my money around more than once or twice a year. But, with my considerable money market exposure, "you're avoiding short term market risk, but taking on a high amount of inflation risk and your investments are not growing fast enough to keep up with the cost increase," says Ritter.