Make a loop
Place the ball end of the yarn under the loop you have just made
Insert the hook under the yarn you have just placed under your loop
Pull the hook and yarn to one side
Yarn around hook
Pull the hook and the yarn through the loop
Place the hook through the loop in your hand from the front
Wrap the yarn around the hook
Pull under the loop in your hand
Wrap the yarn around the hook and pull the yarn through both the loops on your hook. This makes a single crochet (UK double crochet).
Carry on making single crochets in the same way. Usually 6 single crochets are made for amigurumi's.
When you have made the correct amount of stitches pull the tail end of the yarn tight until there is no hole visible in the middle.
To make your first round insert your hook into the next stitch
Make a single crochet
Place a stitch marker on the double crochet you have just made. This marks that this is the first stitch of the round.
Carry on making single crochets till you get to the stitch with the stitch marker on. This is 1 round.
Remove the stitch marker and make the first stitch of the next round. Replace the stitch marker on the stitch you have just made. Carry on in this way making the number of rounds you need.