How to make an increase? Step-by-step tutorial with photos

Increasing is one of the most important techniques in making amigurumi. It is so important, in fact, that without its use it will not be possible to make any toy. Fortunately, increasing is very simple it simply involves making two single crochet sitches (or any other stitch for that matter) in the same stitch.

Insert the crochet hook under both loops of the previous stitch.
Yarn over or yarn under depending on whether you want to make a V-shaped or an X-shaped single crochet stitch.
Pull the yarn through the first loop on the hook. We now have two loops on the hook.
Yarn over.
Pull the yarn through the two loop on the hook. 
Insert the crochet hook under both loops of the same stitch.
Yarn over or yarn under depending on whether you want to make a V-shaped or an X-shaped single crochet stitch.
Pull the yarn through the first loop on the hook. We now have two loops on the hook.
Yarn over.
Pull the yarn through the two loop on the hook. 
Ready!