Low ACoS: if ACoS < Target ACoS after 1 Order --> increase bid by 30% (max: 1.25)
0 Sales: if orders = 0 after 1,5X clicks --> pause Keyword
A more agressive strategy could additionally include the following rule, which may be quite costly though as it will usually increase the bids of several long-tail keywords:
Low Impressions: if impressions < 300 after 7 days --> increase bid by 20%
0 Sales: If 0 sales after 20 clicks --> negative searchterm (exact)
Low ACoS: If ACoS < Target ACoS after 150 clicks > increase Adgroup Bid by 20%
High ACoS If ACoS > Target ACoS after 150 clicks > decrease Adgroup Bid by 20%
Defensive vs Aggressive Rule-Sets
Depending on your strategy, you may want to be less or more aggressive - for instance to help push the keyword rankings of new products.
A more defensive strategy could mean decreasing bids by a higher % (eg. 30), while a more offensive strategy could mean the same for increasing bids.
This article (click here) explains how to determine the Target ACOS.
This article (click here) explains what 1X/1,5X means, ie. how many clicks you should wait.