How do I file taxes from previous years?

Answer 1

You can access the forms needed for prior years here

http://www.irs.gov/formspubs/article/0,,id=98339,00.html

If you need the income information for the missing years you can call the IRS at 1-800-829-1040 to request transcripts of your information, they will need to verify your identity before accessing your account. These can be mailed to you within 7 to 10 days.
Mail the returns, if you owe on them pay the amounts in full if possible. if you are not able to pay a payment plan can be set up

Depending on the years not filed if you have a refund coming for years prior to 2003 the refunds are gone, You have until April 15,2007 to file the 2003 return in order to get the refund for that year.

Answer 2

You have to file on paper. Just get back tax forms by calling the irs direct or going to your local library. Just file as you normally would have and mail in. If you are due a refund, you will get it. However if you owe there will be penalties and interest added to it. If you cannot pay all of what you owe, call the IRS right a way and make arrangements to pay. They will work with you.

Answer 3

Honestly, the best thing to do is to confer with a Tax Professional. If you are not sure, you can check with such organizations as National Association of Tax Professionals, this is a large organization with members of all levels of Tax Professional.
It is worth while to have a decent tax person, because it can set you right on track and make the following years more pleasant at Tax Time.

good luck & blessings