Iron-on transfers designed to print out at home are readily available and easy to use, but do require your home printer to be set up to print images correctly--namely backwards and in with a good density of ink. Printer settings for printing iron-on transfers will vary depending on the printer you use, but most are similar enough that you can choose the right setting for any brand and model of printer even if you do not have the instructions that came with the transfer paper.
Choose the setting in your printer's dialog box that will reverse an image. It is usually called "Mirror," "Flip," or "Reverse." Some printers have setting options that specifically say "T-shirt Transfer Sheet" or "Back Print Film" as well. Choosing one of these options will ensure that when you iron the design onto the T-shirt the image, including any text, will not appear backwards.
Test your image by printing it on a plain piece of paper to make sure the image looks how you want it.
Set the printer settings to the highest dpi (dots per inch) that it is capable of creating. This will create a more color-saturated print.
Choose the paper settings available for your printer designed for transfer paper. Some printers will have a specific "T-shirt Transfer" option, so if that choice is available select it. If it is not, then choose either "High Quality Glossy Paper" or "Special Coated Paper" in the printer's dialog box. You are now ready to print on your iron-on transfer paper.