It's happened to all of us. We tear a bag off the roll to put our produce in and struggle to get the darn thing open. Perhaps you use the lick your fingers method and go after the opening. Perhaps you rub the bag between your hands. Things to be considered before you try these methods.
1: The handles of the shopping carts and baskets are laden with filth and germs. Licking your fingers transfers this to your mouth.
2: If you have already selected your produce know that it hasn't been washed. Also consider how many other people have touched it first; from other customers to the produce staff. Did they wash their hands properly before touching it?
3: The rolls of bags themselves may have been in contact with the floor or other surface before being put out for use.
How do I know this? I was employed in a grocery store for many years and you would not believe some of the things that go on. But have no fear there is a way to open the bag without resorting to saliva or wadding the bag into a ball.
In the picture above (I know it's a crappy picture) if you look very carefully where the arrow is pointing you might notice that the sides of the bag on one side are not completely even. This is not a machine flaw but is done intentionally. This edge separates easily allowing one's finger to slide the side open. Why would I want to open the side when I need to put my produce in the opening in the top you ask? Because it allows you to get your finger through the handle.
Once the handle is pulled open the top of the bag also opens making it easy for use.
I hope this has been helpful to everyone. Less frustration, less germs, happier people!