[header] How to invest in 401 k [title] Know your limits. [step] The internal revenue service (irs) establishes the maximum individuals can contribute to their 401 k every year. Your employer might also impose limits on you. 
[substeps] Check the irs website for limits, which can change from one tax year to the next. For example, in 2013 investors under 50 were able to save up to $17 , 500 in pretax dollars through a 401k.