Slip knots are very useful in knitting and crochet. A slip knot is a quick way of securing a loop of yarn to a needle or hook, and is one of those knots that gets tighter the more it’s pulled. (Here’s some knot trivia: the slip knot and noose knot are very similar and are often confused.)
There are several ways to make a slip knot. This is the one I usually use. I find it simple and visual, which is handy for teaching kids how to make a slip knot.
Make a loop. Where the yarn crosses itself to close the loop, the tail end should be on top:
Take the tail of the yarn across the back of the loop:
With your crochet hook (or knitting needle), pick up the center strand:
Hold both ends of the yarn so the knot doesn’t fall apart, and pull the tail end to tighten the knot towards the hook or needle:
Go gently; it’s easy to over tighten a slip knot. Remember to keep it slack enough to fit a crochet hook (or knitting needle) through.