At the beginning of season there is no way to avoid bidding wars if you really need the player coz everybody else also need that player.

The thing you can do is set yourself some restrictions on amount of tokens you are willing to spend.

Bid early and then see if many are bidding after 2nd or 3rd round. If there are more than 3-4 people bidding after 3rd round then you know its time to stop.

There is no method that will work all the time you just have to ask yourself if you can expend with those tokens or not.