7/21/14 edit: I made this 4 years ago, and dA has changed a lot since then! I don't go on very often, so I recommend you take a look at their FAQs to figure out their ever-changing thumb policies. (I would link a FAQ myself, but the link would probably be dead and/or replaced shortly...)
10/15/12 Edit: To post a big thumb, just add "big" after the first colon in the thumb code. Example: :bigthumb######:
Also, dA has since added another thumb code source below in the "details" section on the right side--it's the same exact code that you'll get from using the dropdown method shown in the sceenshot.
A lot of people seem to be confused about how to send thumbs to enter my contests, so I've decided to make a super simple tutorial!
To post a thumb of a deviation, copy the code inside the box ( :thumb#########: ) circled in red in the screenshot. Everyone can use them in:
Deviation thumbshare forum
NotesOnly premium members can use them in:
Artist's descriptions (like this one)They cannot be used (by anyone) in:
Let me know if I forgot anything!
Here's a thumb!