GIGGAG collected a few simple hacks that fit into this category perfectly.
If you’re still not convinced or if you’re having trouble getting it to work, take these points into consideration:
Make sure the pencil is free from oil. There may be a thin layer of glue on the lead that prevents contact, so just scribble on a piece of paper to get rid of that. Make sure your pencil is made from graphite and not another composite or recycled material (green/eco pencils). Make the groove closer to the tip to improve contact.
Preview photo credit 20jlamorticella/imgur