I sold quite a few things on CL in the last 2 months- an old project motorcycle, a pygmy billy goat, a cow calf pair, some older bridles and an older Lamb brand saddle, an ATV rear axle. Most of it sold within 2 days of posting the ad (the cow calf pair took about 8 days) with very little haggling. I think part of my luck has to do with taking pictures- I always post at least 2 pictures of each item.
I also have a prepaid cell phone number that I list as well as email (I check it frequently). I state in the ad that I have no voice mail and that 4pm-8pm is the best time to call (I leave the phone off the rest of the time).
My typical policy is that I answer the calls/emails in the order that they are received and I will hold an item for as long as it takes the person to drive to see it (typically less than 2 hours)- but no longer. If someone says they want to wait to come look at the item on the weekend, I tell them that it is first come, first served.
If I get lowballed, I just politely tell the person that I'll keep their offer in mind but that I just listed it a few days ago so I'll wait to see if I get any better offers.