It's important to figure out your c

It's important to figure out your central character and layout within your sketch. I like sketching within Adobe Illustrator CC itself (though you can import a sketch as well). Using the Paintbrush Tool (B) with Fidelity set to Smooth in the Paintbrush Tool Options panel and a default Calligraphic brush selected, I've drawn out an excited cartoon character and blocked in the cereal's name above him.

For a detailed guide to drawing the hands, take a look at Cartoon Fundamentals: How to Draw Cartoon Hands by Carlos Gomes Cabral.