what is the standard real estate agent commission in Lake County, IL

Commissions are completely negotiable and they commonly vary by area. In my area, I'd say the ones that I see the most run between 5-6%, but there are also some local agents I've seen that are 4%.

You have to interview any agent and make your decision based on a combination of quality, professionalism and the commission cost.

There is no 'Standard'.  Don't let anyone tell you that 'this is normal for our area' either.  Brokers can charge any commission they and you agree on though many offices have 'minimums'.  It takes much less to market your home today than it did just a few years ago.  The Internet has leveled the playing field. A local company will give you just as much exposure as a national brand. You no longer need to pay 6% to get your property exposed to millions of potential buyers. On the flip side be carefull of the 'list and forget' brokers that take a very small fee upfront and then put the burden of marketing, selling and negotiating in your hands. Don;t pay for anything 'up front' when no one has sold anything. What is important is making sure 1) you are offering out a decnt cooperating commission (ie for the buyer agent) and 2) Making sure your listing agent is getting enough commission to stay motivated, market your place, follow up with showings etc. and 3) Pricing your place right.  Interview 3 or 4 EXPERIENCED agents and compare.  Don't pay extra because you see someone's face in the newspaper.  Their name or image does nothing to sell your place.  The MLS and the related sites (ie Realtor.com) containing your property info is most important.  In this market you certainly want a Full Service Broker but, you do not have to pay full price to get that :)  -Good Luck.