The Chain Stitch

Almost all crochet starts with a base (or foundation) chain. This is the equivalent of 'casting on' in knitting. The base chain is a series of chain stitches, which normally begin with a loop secured by a slip knot.

Slip Knot

a: Make a loop; hook another loop through it. b: Tighten gently and slide the knot up to the hook.

Chain Stitch (ch)

a: Wrap the yarn over the hook in an anticlockwise direction (or hold the yarn still and manoeuvre the hook); b: draw the yarn through to form a new loop without tightening up the previous one.
Note: Unless otherwise specified, always wrap the yarn this way round.
To make a length of base chain, make as many chains as required. Hint: Keep shifting your left hand position up close to the hook every couple of stitches or so; this is easy, if you use a right hand finger tip to hold down the loop on the hook, while you do so.
To count chains correctly as you make them, do not count the initial slip loop as a chain. To count them afterwards, first make sure that they are not twisted and that you are looking at the 'front' c: then count back, but ignore the loop still on the hook.