Don't put your 401(k) contributions into your company stock. I know it sounds tempting because your company is fantastic and is better than anyone else's and all the hype within your company about how good your company's long term prospects are makes it appear to be a mistake not to invest your 401(k) contributions in you own company.

But keep in mind that they are most likely matching your 401(k) contributions with company stock. This already will be a big portion of your 401(k) portfolio that has specific risk.  This, plus the fact that you also depend on the company for your livelihood is already enough eggs in that basket.

Instead of investing your 401(k) contribution amount into your company stock, invest your contribution into the funds they offer inside the 401(k).

Choose which fund in the 401(k) based on your time horizon.  You should pick the risky stock fund if you time horizon is long, and blend into the safer funds as you time horizon approaches short term.