A 6% fee is common in my market but I read somewhere the national average is around 5% (I think it was Clark Howard's website). In most cases the commission is split 4 ways, The Selling agency (company) and Listing agency (company) split the fee. Then the fee is split again between the agency (company) and the working agent (the one whose face is seen during the transaction). It happens this way because a listed property placed on the Mutiple Listing System or MLS is visibly available to sell by any agent (1200 in my market) participating in the MLS. It is a very powerful and effective sales platform.
Does the buyer or the seller pay? It's really semantics; the seller often pays the fee out of closing proceeds but the buyer is paying for the home which has a commission/fee built into the price. You could really argue that either or both parties pay.
The best way to determine what commission/fee to pay is to interview several agents in your area. Remember the fee is negotiable. I wouldn't pick based on price only but how the agent will insure your house gets the proper market exposure.
I am a practicing real estate agent in Fayetteville North Carolina