I would advise someone to get a second job before I would advise them to take money out of their 401(k) unless it is a medical or other very serious emergency, that is unless they are a single parent. That applies whether you are still employed there or have left the company.
Don't take retirement funds out to pay bills, pay off credit cards or buy a new car. I am not a fan of taking out retirement plan investments for a home down payment or education expenses, either, unless a very high income is in store that can rapidly replace it.
A retirement plan is not a savings plan for paying bills or big expenses. It is a long-term vehicle, and to treat it otherwise is nearly always to harm your retirement. When you have to start over, you have cut off the "mountain" part of those long-term compounding growth charts.
While that sounds harsh, I am trying to keep you from joining the vast army of Americans that have nothing but a meager Social Security check at retirement. That is not the way to spend your 20 or so retirement years. Ask any senior citizen.
As an adviser to retirement plans, it kills me to see how many people pull money from their plans. Resist the temptation and buckle down, that is, unless it is a true, unavoidable emergency and there is no other option.
I would start by talking to the HR department at your previous employer. They should be able to put you in touch with the Administrator of your 401(k). The administrator of the 401(k) will be able to set up withdrawals. If you have the Summary Plan Document, it should explain what types of withdrawal options you have and who to contact.
Curt is right, you need to get a copy of your Summary Plan Description because Plan Sponsors have quite a few options when it comes to how they allow withdrawal of 401(k) balances.
If you have terminated employment from your employer you can take a withdrawal of your vested account balance but your options may include lump-sum, installment, and partial or as requested.
If you are still employed by the Sponsor then you may be able to take a withdrawal for the following reasons: - Hardship, but certain IRS rules must be met to qualify and you can usually only withdraw your own employee contributions. - Loan up to 50% of your vested balance or $50,000, whichever is less. - In-service after a certain age chosen by your employer when they set up the plan. Each of these options, if available to you, has pros and cons and you should speak to a financial professional or your tax advisor before you make your decision of which method to use.
Having said this, if you are not in retirement, I would encourage you to try to avoid raiding your retirement account prior to retirement unless you have sufficient funds saved elsewhere to close any gap between your spending in retirement and your social security and pension payments (if any).
Hope this helps.