Collect reference pictures -- photos or illustrations -- that fit your design theme.
Make rough sketches of your design ideas, using your reference pictures. Don't be afraid to use a few sheets of paper to work out design and composition problems. This is the time to experiment with different image or font combinations. The more you work out in this stage, the easier the later stages will be.
Draw your final designs on paper or create them in a design program like Adobe Photoshop, Microsoft Publisher or Corel Draw. Use the graphics software that you are most familiar with; the end product will turn out better. This version of the image will be full-color and should be the most detailed of all of your drawings, because it will be the final image that will end up on your T-shirt. Make sure that your final drawings fit the specs for the iron-on transfer paper. You may not want a drawing that measures any larger across than 7½-inches by 10½-inches.
Scan the drawing into your computer using a flatbed scanner and the software that came with the scanner. Follow the instructions that came with the scanner. Set the scanner to 600 dpi (dots per inch). Most standard scans range from 150 to 300 dpi; however, this scan range will ensure that your fine line art will import into your computer minus many of the visual flaws that come with scanning line art at a lower resolution. If you created the image in a compute program instead of by hand, you can skip the scanning step and go straight to saving the file on your computer.
Save the scan to your computer in a file folder. It's helpful to keep all your related files in the same folder.
Insert iron-on transfer paper into your printer, following the instructions that came with the paper.
Flip the image vertically if the words are backward. Most design programs have this option in the "Print" menu or under a heading like "Image".
Print the image out. To do this, go to the "File" menu and then go to "Print". A pop-up window will come up. When it does, hit "Print". The image should print onto the iron-on paper.
Follow the instructions that came with the transfer paper package to iron it onto your T-shirt.