Some recommendations:
1- Both be on at the same time to do the transaction: using steam messaging or going into the cRPG IRC channel and opening up a private query between both of you are probably the best two ways, because if anything goes wrong you have evidence in writing.
2- Make sure trades that are put up on the market are not appealing for others to snatch up. For example, if you are selling your loompoint to someone for 500k and they are giving you their +2 loom to turn into a +3, don't put anything up that someone else could see as a good deal and snatch from you guys. Put up a trade offering stones for 500k, then a trade offering a felt cap for their loomed item, things like that. Then after you loom the item they will put up an offer of stones or whatever requesting a +3 item.
3- Make sure you have agreed on what item needs to be loomed before you do the trade... if someone wants a high tier bow loomed and you don't have any power draw you won't be able to loom their item and it will just be a waste of time.
4- Don't try to scam. The cRPG community is small and your reputation is everything. Besides, it's stupid because Meow will find you. He knows... he always knows.