If you happen to have wobbly aligator clip then electrical tape will fix most of the issue, but it not a permanent solution. If you used them for a long time I can suggest getting new ones. You can check them out in our Store. 

But if you are in the hurry and your experiments can't wait that long then the quickest solutions besides electrical tape would be buying new aligator clips from your local hardware store & soldering them to the cable.