The start ring will be used to crochet in rounds. This is necessary for crochet pieces of motives, scarfs, tablecloths, amigurumis, decoration and many other things. You have 2 possibilities to make a start ring.
The yarn ring (also known as Magic ring). The reason behind is to start the work not with a straight chain instead you start with a ring. This ring you can pull close without a hole.
Start ring with a chain
In this case, you crochet a chain of five to six chain (the number of chains depends on the work you do and may vary). This chain will be closed with a slip stitch to a ring.
We start with the chain:
Yarn around the pointer finger of the left hand,
Push the crochet hook underneath the string and turn.
Get the yarn and pull it through the loop.
The first chain is done. Now we can crochet ahead with the chain.
Again yarn over and pull it through the first,
Now we form the next loop.
*Yarn over and pull it again through the loop *
Repeat step from * to * as often as you need.
Now you form a chain of chains.
With the hook into the 1st chain of the chain,
And pull it through both loops.
Now you can crochet single crochet, double crochet etc. into the ring.
As example I show it with single crochet.