First thing's first, only attorneys or accredited representatives working for the Board of Immigration Appeals (BIA) can give you legal advice for immigration matters.
Don't pay for blank USCIS forms - you can get them for free on USCIS's website!
Be wary of businesss, or even attorneys that guarantee that they'll get you a visa, green card or other immigration documents. In the law, there are no guarantees, and any good lawyer would tell you that.
Keep an eye out for Notarios publico, since, in the U.S they aren't authorized to give legal advice regarding immigration.
Don't listen to what your friends say (unless they are an attorney!) If you're looking for legal advice, be careful and make sure that the person you're seeking your advice from is authorized to give you that advice, otherwise you can be in a world of trouble down the line just because you're trying to save some $$ right now.
If you have an immigration question or issue, you should speak with an immigration attorney.