Timing is key for me. For instance there will be more people on the game between say 5pm and 10pm than there will in the early hours of the morning.
Always have lots of tokens when bidding for players as having just 10-20 might not be enough. The most ive lost in a bidding war was 36 T!
Also i was bidding with this other guy and he had 3.5M cash and i had over 5M cash yet he still bid more than the 3.5M he had! How is this possible?