Everyone benefits from trading. Veteran collectors try to bolster their trading lists so that will have something of interest to someone else with a trader. Both parties get something new in a trade. Once you have items for trade, make a list. Each item on the list should be described to the best of your ability.
Excruciating detail is better than terse or ambiguous statements and is much appreciated.
Identify each item. Name the maker, the model, the approximate date of manufacture and any published references to the key. Describe the condition and note any broken or missing parts. Neither party wants a surprise in a trade. At the end of your list, describe items that you are looking for in trade.