In frustration once, I painted a wide strip of runner cement down the middle of my ruler...and let it dry---took about 2 minutes. Works like a charm!

Any LQS, Hobby Lobby, Hancocks, or Joanns should have the Invisagrip, sandpaper or clear dots.

I use the sandpaper dots, but they aren't always in the right place, so I think I'm going to get some of that invisigrip stuff!

I found some ruler grippy dots at Joanne's in the notions section that you stick on your ruler. It works really well. You can't slide your ruler on the fabric to line it up though....it moves the material. You have to pick ruler up completely to re-position it.

go to dollar tree and buy a roll of rubbery cabinet drawer liner cut a strip and it works well....

After reading all these good hints, I will share mine. A friend told me if you put your little finger off of the ruler and on the cutting table it does help to keep it from slipping.I hope you can understand this.
Pickle

I use sandpaper dots. I put one in each corner and then if its a ruler i put 2 diagonally from each other. But it its a sqaure I put them in each corner and one on each side.

I use a "O'LIPFA Lip Edge Ruler" that I've had for years. But I did have trouble when cutting multiple layers that the ruler would not stay put on the edge of my cutting mat. To solve this problem I glued a carpenter's pencil (can be found at any home improvement store) on the lip. In case you're not familiar with the pencil - it's flat and does not have an eraser or any metal and can be cut easily to any size.

Invisi-grip. comes in a roll looks like heavy contact paper get it in quilt shops or Joanns or Handcocks.
I use it on all my rulers. Otherwise the little round sand paper dots you put on back. I don't like the clear plastic dots. They are too thick.

thanks.