You post up unID'd ilvl63/ilvl62(such as demon hunter cloaks that max at ilvl62) and you list next to it what ilvl63 items you need instead. This way we all have better chances of getting upgrades that we want. For instance:
WTT: ilvl63 pants for ilvl63 shoulders.
Please update your original post once you have made the trade so that we know they are not available anymore.
Don't forget to post your battletag so people can contact you, or if you would rather have people PM you, say so.