Here are just a few examples of the many, many, horrible FSBO signs I've seen.  You don't see agents doing this so why should you do it??  This is what buyers think when they see these:

"If they were too cheap to buy a decent sign, I wonder how cheap they decided to be on maintenance?"

Never write extra info on the sign!  It's extremely tacky.  This is what sign riders, flyers and flyer tubes are for.

  Magic marker, duct tape and poster board rarely inspires the confidence of prospective buyers.

"Hand Painted" is not a feature home buyers are always willing to pay more for.

 This sign should really bring in the high rollers!

Need I Say More?