Step 2: Find a Subject
When selecting a subject consider what is around and behind it. The more isolated your subject the better. When you 'paint with light' everything your light touches will be illuminated. If the light spills onto other objects around or behind your subject they will be illuminated as well, distracting from the subject.
Also consider movement. When using the log exposures required for this technique any movement will blur, even slight ones you may not immediately notice.
Take note of this image as it represents the tree 'unpainted'. This image features the same 30 second exposure as most of the following examples