Some more things to note:
If you're arranging trades with several people, clutter can amass quickly. This makes your thread difficult to navigate for you and your clients, so it is in your best interest to make each and every post count. Specifically:
-Refrain from filling topics up with off-topic conversation. The forum is for trading.
-Don't be afraid to use Private Messages! Things like arranging times, notifying the trader that you are online, etc. are more suited to PMs, as it doesn't contribute much to your thread and just makes things messier for everyone else.
-Keep important contact information easily visible in your first post! This includes but is not limited to friend codes and time zones. This will save you and everyone else time, and again prevent clutter.
Clutter is the main issue here. As threads fill up they become more difficult to use, and that's not something anybody wants, so do your best to avoid that. As a topic owner, don't be afraid to impose rules upon those posting in your thread. The neater, the better!
No, this doesn't mean your thread will be locked for a single "violation" of space wasting. This isn't a communist state, but it can become one if people don't use discretion.