There are plenty of wood fillers on the market and they work fine, but what if you only need a little and you need it right this minute. It's going to take you a minimum of 35 minutes to drive to the local building center and back just to buy it. You already know most of it will end up drying out before you get to use even a quarter of it. Well, you can stay home in your woodworking shop and make your own wood filler. It's so easy it's practically child's play.
Go to the power saw or power sander you've been using for the current project. Use a clean paint brush to sweep sawdust and/or sanding dust into a paper cup. If you can't find any, cut some wood on the table saw or radial arm saw and collect the sawdust from that. Or sand some wood and collect the dust from that.
Squeeze wood glue over the wood dust in the paper cup. Stir the glue and dust together to create a thick paste.
Scoop the homemade wood grain filler up with a 1 1/2-inch putty knife. Work the wood filler into the hole or crack in the wood you need to fill. Let it dry before sanding off the excess from the surface of the wood.