Decide which idea to use for your embroidery and where the design will fit. This way you will be sure of its size. Know how to change the size of your embroidery in case you make a mistake while measuring. Browse through tattoo books or the Internet for design ideas. Shop craft stores like Beverly's or Michaels for cool threads and other materials.
Draw your design before you start to stitch. Look it over again and again to be sure where each stitch will go. Decide the color coordination and the stitches you will use beforehand. It's important to be comfortable with your design so you don't mess it up when you are actually sewing it on your shoes.
Get your shoes ready. If they look really dirty, wash them before you start embroidering. If you see a lot of creases on your sneakers, iron them. Good embroidery requires wrinkle-free shoes.
Check your work frequently to make sure it matches your design. Since freehand designs are difficult to create, don't try to get your embroidery to match up perfectly with your sketch. Consider using an iron-on embroidery design instead. It's much easier to follow iron-on designs so you will make fewer mistakes.
Tighten the fabric on old shoes with an embroidery hoop. Old sneakers have loose fabric because of daily use and multiple wash cycles. After tightening, the fabric will be easier to stitch on. You won't need an embroidery hoop if the shoes are brand new.