I want to extend my stay in U.S.A. how do i consult an immigration lawyer for that.?

consult an attorney

http://jakemanlaw.com/

it is a very good firm for lawyers ..start your application as early as possible before your stay expires.

submit some type of evidences for your extension such as

documents showing the reason for your extended visit ( such as medical records, police reports documenting an emergency, letters from U.S. relatives who need you to remain longer than expected)

Well, it depends on what basis you are in the US currently. For example, you cannot extend your stay if you entered under the Visa Waiwer program. Anyway, look in the phone book under "immigration lawyers", pick one and make an appointment. You will have to pay.

You need a lawyer to fill out a simple form, put it in an envelope, and mail it?

If you entered under the Visa Waiver Program, you can't extend. If you entered with a visa, and are still in status, you'll file an I-539 with the USCIS.

http://www.uscis.gov/i-539

Depends on what kind of visa you have, and your reasons for attempting to extend your stay. If you are on Visa Waiver (ESTA), there is absolutely NO way to extend your visa or change to another visa without returning home. If you overstay so much as a day, you lose ESTA privileges forever.

Tourist visa: must apply at least 45 days in advance. Rarely granted.

Student: must still be a full-time student in good standing and making required progress toward your degree.

Employment: only qualified employers can apply for employment visas for their qualified employees. If the employer wants to retain that employee for another term, the employer must apply.

So what kind of visa do you hold, and why do you want to remain in the US for how long to do what?

It is a simple application. A lawyer is not needed. See this: http://www.uscis.gov/i-539

Marry a homeless person. Simples

success is rare on a B-2 .visa ...and you could lose the visa ...

on a visa waiver its not possible at all