Many crochet projects require start crocheting in a round, for example, Amigurumi(Japanese art of knitting or crocheting small stuffed animals and anthropomorphic creatures), coasters, containers, hats, doily, individual pattern for crochet patchwork projects etc.
In general, there are 3 ways of doing this. Some people might have developed their own method.
Start with Multiple Chain stitchesUse multiple chain stitches to form a loop, e.g. use 6 or 8 ch. Example below is using 8 ch.
* picture is taken from KAGIBARI AMI NANDEMO Q&A - KONNATOKIANNATOKI Copyright© N.Seto 2003
Start from a slip knot then make 8 ch (chain stitich), use sl st(slip stitch) from the first ch to form a loop.
The disadvange of this method is the hole in the middle is quite big and not adjustable.
Start with single chain stitch
Use the first ch(chain stitich) as a loop.
* picture is taken from My First Love of Crocheting, author: Pan Meiling, published by www.winfortune.com.tw
The hole in the middle is smaller using this method.
Start with double ringThis is my favourite method. It used frequently in Japanese crochet projects.
* The demo picture below is taken from http://i-s.milkcafe.to/ami/kiso/ichiniju.html
1. Wrap the yarn twice around your finger (I usually wrap it around my two fingers instead).
2. Carefully took off the created loops and use two fingers to pinch them. Crochet the yarn out of the loop.
3. Then make a ch(chain stitch), note: this ch is not counted as one stitich in the 1st row. It just an upright stitch. Use the left hand finger to pull the yarn to control the tightness of the base of this ch.
4. Now start to crochet a sc(single stitch).
Now the first stitch of the 1st row is finished. Continue crochet 5 sc if the 1st row requires 6 stitches.
Next step is to adjust the loop. The left hand side thread is connect to the yarn ball, I named it T1. In the loop itself there are two threads, I named it T2 and T3. You need to pull one of them(T2 or T3) to tighten the loop. To find out which one you need to pull, slightly pull the left hand side yarn thread T1, don't pull too much, just pull it little bit so you can notice one of the yarn thread in the loop get tighter, assume it's T2, this is the thread you need to pull to make the loop smaller. So pull T2 and after the loop is minimized, you can see that T3 is the remaining thread in the loop, pull T1 again which will then tighten up the this remaining thead in the loop.
Then do a sl st(slip stitch) from the first ch(marked in green below) to form the circle. I normally will pull this sl st stitch tighter so it won't be too obvious and the project will look better.