Make sure the surface you're applying your decal to is clean and dry. Soapy water or rubbing alcohol work well. Be sure to let it dry completely!
Make sure there's room for your decal and that it aligns correctly.
Be sure to leave the decal attached to the transfer tape (the clear sheet with gridlines). If the decal doesn't come up witht the transfer tape, use a firm, flat surface (like the edge of a credit card) to make sure the transfer tape stick to the vinyl.
Be sure the decal is aligned and positioned exactly where you want it before you let it touch the surface. Use the grid lines on the transfer tape as a visual indicator to check position and alignment.
Use a firm, flat surface (like the edge of a credit card) and to run over the front of the decal to ensure it adheres completely to the backing surface. Work out any air bubbles and take special care with small pieces of stickers and design.
Carefully remove the transfer tape from the decal. If any part of the decal comes up with the transfer tape, ease the decal back down into place with the transfer tape and repeat step five to ensure the decal sticks to the surface. Slow and steady is the key here.
Use your finger to make sure there are no bubbles or loose edges to you decal that can get caught or pull away from the surface.
Let the decal sit for 24-48 hours to completely adhere to the surface. If applying to a tumbler or in a location exposed to the elements, make sure the decal stays clean and dry for 24-48 hours before getting wet.