Here's my legend for Trello project boards:

Columns:
- **Plan**: General ideas/discusion of features and changes related to project.
- **Queue**: Features and changes that are queued to be worked on
- **Do**: Tasks currently being worked on, usually assigned to person or undergoing testing.
- **Fix**: Bug queue
- **Pend**: Functional but needing iteration and testing.
- **Show**: Completed tasks

Cards can contain more than 1 related task, in the form of checklists (either trello or markdown).  You do not need to separate these into individual cards until it becomes organizationally better to do so.

Priorities:
- [H]igh
- Normal (default, don't list)
- [L]ow
- [F]uture: Things that may be important to think about now, but are otherwise far off.
- [P]ending: Task is postponed or pending something.  (Considering using [W])

Difficulty:
- [T]rivial or [E]asy
- Normal (default, don't list)
- [D]ifficult
- [?] Uncertain

Other:
- [W]aiting on tag (use [W:tag] and #tag on card title or checklist task).  Tags can be features or versions.

Example for high priority, easy difficulty, waiting on #1.0 tag:
```
[H][E][W:#1.0] Card Title
```