Radon testing a basement

Before I decide to install a radon fan in my basement, I need have the space tested for radon. What is the best way to do this? I was thinking of getting a Geiger counter or a home radon inspection kit (though I've read that these are not accurate). Some friends said that the best, most accurate way to figure this all out would be to hiring a licensed home inspector to do a radon check. Specifically, I believe that there is radon in my granite countertop. According to the EPA, radon levels less than 4 pCi/L still pose a risk, and in many cases, may be reduced. And they also recommend taking action if radon gas levels in the home exceeds 4 picocuries per liter of air. Will a radon fan take care of this problem? Thanks for any recommendations.

rodi791, I think your friends are right. I also heard (at least where I live) that this testing is done by the municipality for free. I don't know if this is the case in the U.S.

I don't think a radon fan is effective but this is ONLY my personal opinion and not based on scientific tests.