I am a single parent and I need help completing the W-4. I want to ensure that I get most benefit out of it. I claimed too many allowances in the past and now that I have a dependent, I want to make sure I see the full benefits come tax time.

What do you mean by "get most benefit out of it"?

If you claim more allowances on W4, your employer will deduct less taxes from your paycheck. Withholding by the employer is not the actual taxes as per your tax return. If withholdings are less than your tax as per your tax return, you must pay the tax due.

If you claim less allowances than required, you will get a refund when you file your tax return.
Read: Your U.S. Tax Return: Filing W4 Employee's Withholding Allowance Certificate (http://taxipay.blogspot.com/2008/02/filing-w4-employees-withholding.html)

I have had to pay taxes in the past for taking too many allowances. That is what I mean by "most benefit". I also want to know about EIC and how it works. Is there a separate form?

From a money management point of view, you WANT to pay come tax time, just as long as you do not incur an under-withholding penalty.

Always remember: ANY refund is an interest-free loan to the government!

The money you get back in a refund is YOUR MONEY which you over-paid by over-withholding from your weekly/bi-weekly/monthly salary.

Undoubtedly, you have BETTER uses for your money than to give it to the government to use at no cost to the government.

If you can manage your money to write a check of $1,000 or less come April 15th, then continue to do so.