Some guidelines for leaving feedback for other members. In other words, what kind of information is useful for other members.
1) What kind of deal you had. Please, keep it short but informative.
"I bought some G2 figures from X."
"We made a small part trade."
"I sold two Energon figures for X."
2) How did the deal go.
2.1) If everything went well, please mention it clearly.
"Trade went well, parts arrived safely and fast. Toys were well packed."
"Prompt payment, good communication."
2.2) It is also possible to leave negative feedback, but keep it civil. In this case the member getting negative feedback has possibility to answer to feedback. In other words give his/hers point of view what happened. If necessary, the one giving negative feedback can comment that, but no more messages after that. Feedback thread is NOT meant for discussing and/or arguing!
"The toys I bought arrived fast, but were in considerably worse condition than described. Despite that, seller refused to cancel the deal."
3) When did the deal happen.
Note also that it's useful to leave feedback of new deals, even if you have left feedback for the same member before.
ps. If someone you've made a deal with hasn't remembered to give you feedback, it's more polite to remind him/her by PM than publicly...