The idea is that if it looks hard to steal, only the most desperate or skilled crooks will bother. Laptop cables come in all shapes and sizes and are available almost everywhere. You get what you pay for, so don't scrimp. You also need to shop carefully on the off chance that a particular lock won't fit your laptop. If you have a newer laptop, attach the cable via the security slot.
Older models rely on a PC card slot or use an adhesive.
One even attaches to an eight-pin connector. Once you've attached the cable to your laptop, you need to wrap the cable around something that's hard to move and difficult to destroy. Desks and Sherman tanks come to mind. For those of you who live in more prestigious ZIP codes, a good cable will probably keep your laptops safe and sound. You might also consider a laptop alarm.