When I sit down to trade, I really sit down to trade. I want to get as much done as possible. Its easy to get caught up in sending out a bunch of trades at a time.
That being said, dont offer the same card over and over again – even if its with different traders. Pending offers will stack up, and if someone accepts – all that work you did will be gone. Once the card is accepted, even if you have multiples, the rest of the trades will be voided.
Diversify your offers!