Your 401k is a great tool and you should use it for your retirement planning; but there are better options that would help you even more than your 401k. Once your employer stops matching on top of your contribution you need to move to a better investment vehicle. You need to find yourself an IRA (Individual Retirement Account). There are two kinds of IRAs, a Deductible IRA and a Roth IRA.
A deductible IRA allows you to take a tax deduction on your IRA contribution, which will lower you taxes by your marginal rate. So let us assume you max out your IRA (you can only contribute $5000 to an IRA per year), and you are in the 25% bracket. So take $5000x25%=$1250 reduction in your taxes it works just similarly to the 401k tax deduction. Here is the drawback on the 401k and deductible IRA is that you get growth tax-free until you pull it out then you have to pay taxes.
What would you say if there was a retirement vehicle that you did not have to pay taxes on the growth or on what you pull out of it? There is such a thing; it is called a Roth IRA. With a Roth, you do not get a tax deduction now but you get to grow and withdraw your money tax-free. The only downside is you do not get a tax break now you get it later. The money you contribute is after taxes, but I am almost willing to bet that by the time we get to retirement with the way our government spends money (check out my blog post about our government debt) so the Roth is advantageous to avoid those taxes when we get to retirement.
One thing to remember with all of these retirement vehicles if you pull out the money before 59.5 years old you will pay a 10% penalty and taxes if you have a deductible IRA or a 401k.