A 401k plan is a tax qualified retirement plan sponsored by an employer as part of a benefits package offered to the employees. The payments an employee deposits into the plan are made on a pretax basis. They are not reported to the IRS as taxable income. Any interest, dividends or capital gains on the employee's contributions are also not reported as taxable income. The contributions and earnings are reported as income when they are paid to you.
The first step to get 401k advice is to learn how much risk you are willing to accept in return for potentially greater rewards. A web search of "401k advice" will yield more research resources than most people need. You can do the research yourself if you are so inclined. If you do not want or trust yourself to do the research, you will find plenty of companies and advisers offering assistance in the same web search.
Research what is available in your 401k plan is the next step to get 401k advice. Most employers provide 401k advice and information to their new hires as part of their orientation. If that is not available, contact your employer for more information. If your employer has a benefits department, this will be your company resource for 401k advice. If there is no benefits department, contact human resources, payroll or your supervisor for advice on what is available to you. Many companies have Web sites now that will provide information on the 401k plan and its features.
Now that you have an idea of what type of investor you are, you are ready to evaluate the available options in your employer's plan. Make a list of the available investments, ranking them from least to highest risk. Now just decide what percent of your contributions you want to have in the investments. Remember one of the golden rules of investing is be diversified, never put all your eggs in one basket. If you decide to invest entirely in small company growth funds, divide your contributions between 2 or 3 of these funds. Better still, invest part of your contributions into funds with similar objectives. This way, if one sector goes down your entire portfolio will not be down.
Finally, set up a schedule to review your 401k account. Since this is a long term investment, every 6 to 12 months should be fine. Make adjustments as needed or desired to keep your plan working for you.