Try to limit your absence outside the U.S. to less than six months. If you do, you can easily return to the U.S. without abandoning your green card.

If you stay outside the U.S. for more than six months, things can get tricky. You’ll have to ask for permission to re-enter.
If you are outside the U.S. for more than one year, the U.S. will presume you have abandoned your green card. You can overcome this presumption. However, you can avoid any troubles by getting a re-entry permit.
 Even if you are away for more than a year, you don’t have to give up your green card unless you intend to make a permanent home outside the U.S. Instead, you can get a re-entry permit. You must complete the required paperwork before you leave the U.S.—at least 60 days ahead of time.Obtain Form I-131, which you can download at https://www.uscis.gov/i-131. Get the instructions as well.
Provide two passport-style color photographs of yourself and pay the required fee.
 A qualified immigration attorney can analyze your situation and recommend the best course of action. In the U.S., you can find an immigration attorney by contacting your local bar association and asking for a referral.

You might be surrendering your green card for tax purposes. If so, consult with a tax attorney.
Limit your stay outside the U.S. Let’s say you need to leave the U.S. to visit relatives or go to school.
Get a re-entry permit instead.
Talk with an attorney.
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