Don't forget your old 401(k) that you may have left behind at a previous employer. If the fees are high there, you will want to either:
Review your current investment options and associated expense ratios in your 401(k) plan. Lower your fees by selecting the lower expense investment options in each fund category you use (e.g. large capital stock fund, corporate bonds, etc...)
Selecting the lowest expense funds in your 401(k) account is typically the way to go. As a double check, look at 5 and 10 year returns of the funds in each category and ignore 1 and 3 year returns. Long-term performance will typically align with lower expense funds.