A theme, an entry format and a judging plan for drawing, poster and design contests.
01Make the theme specific
'Bangkok after dark' gives entrants a starting point; 'Art' doesn't. Publish the theme with one or two reference images.
02Fix the format
Say the file type, size and dimensions you'll display: a poster as A3 PDF or a 3000-pixel PNG, for example. It makes the showcase look consistent.
03Be clear about rights
State who owns the work, how you'll display it and whether you'll print it. Entrants care, and it's easier to settle before they submit.
04Plan the reveal
Decide when and where winners are announced, and give them a public moment on the event page.