Iron-on transfers create a refersed image of any design you wish to use, so it's important to trace the pattern in the opposite direction of the final design.
The quickest and simplest way to do this, is to trace the pattern in regular pencil onto a piece of paper. Then, flip the paper over and re-trace using the iron-on transfer pencils.
Remember, transfer pencil pigments are permanent and must be completely covered by embroidery so they are not visible. Keep your pencil sharp and your lines thin for the best coverage.
If you prefer to use a water-soluble, non-permanent transfer method, there are several options available that you can use instead of iron-on transfers.