Many crochet projects start off with a slip knot - so this is one of the first thing that an aspiring crocheter needs to pick up! Fun fact : the slip knot is called such because it can be easily undone by pulling on the tail end. For crochet, the slip knot will form the base for your hook to be inserted to start crocheting.
Here's a video showing how I form a slip knot. This is purposely done slowly so you can follow along with the video.
Next mini lesson : how to hold your yarn.