When my second child would nurse, he liked to yank on my shirt: specifically the collar of my shirt. It annoyed me to no end, so when I got wind of something called a "nursing necklace," I was game to give it a try. Even if I wasn't crafty.
I had to try a few different types of string/lacing before I found something that worked. I ended up using a hemp thread. It is strong enough, and it will usually stay knotted through lots of yanking.
a small collection of large buttons in bright colors
a small collection of pretty beads
a strong string about 24 inches long (I use hemp) - it needs to withstand a lot of pulling!
Double knot one end of the string. Choose a bead to begin with; string it, then knot the string again. I find it very helpful to place a knot between every item on the necklace, that way if the string stretches (as my hemp does), the beads and buttons are still reasonably well-distributed.
Here's where you can get creative. I have chosen a pattern of three wooden beads followed by five buttons. However, part of the fun is making the necklace into what you want it to be.
Continue stringing until the necklace is about the length you desire (you will use a fair amount of the string by making all those knots). Then knot the ends together securely and trim any excess.
I've used a nursing necklace with my last three babes, and fully intend to use it with this one as well. Obviously it's not needed with a newborn, but a few months down the road, it will almost certainly be invaluable.