1. Carefully field-strip the rifle and examine for old built-up cosmoline, especially the gas tube and the bolt. The standard SKS doesn't come with a firing pin spring, so it's possible to experience a slam-fire when you release the bolt if the pin is clogged with cosmoline.
2. Speaking of cosmoline, most (if not all) Yugo SKSs have a grenade launcher attachment and sights. Sometimes the gas vent valve will get blocked with cosmoline, which may cause problems with semi-auto operation.
3. Examine the front sight to ensure it aligns with the rear sight along the length of the rifle. Sometimes, the rifles are reassembled with the front sight canted beyond the sights' ability to correct. Speaking of front sights, an SKS/AK front sight pusher tool is a good thing to have.
Like I said, the SKS is a nice rifle for the cost and a good C&R collection item. Be safe and have fun!
I took extra care cleaning the firing pin. Thanks for the tip. Can't wait to get it to the range!