I've done so many trades over the last few years, I've lost count. On a couple of occasions, I've traded up to eight coins at a time. Only once when I first started trading did I not receive my trade after I had sent mine.
If the person has a few more coins that I am looking for, I don't mind doing a multiple trade as long as that person is reputable. If it is someone new, I,ll start with a single trade and see how that goes.
I say be honest with the people you trade with and that honesty will go a long way. When I receive coins, I always send back an e-mail thanking the person and letting them know that their coin or coins have arrived and I enjoy receiving one also.
Sometimes, mail is slow and it takes time for the package to arrive. If a person inquires on a late arrival, I make sure to let them know that if after a reasonable time, the coin is actually missing, I am willing to replace it.