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 25 clicks --> negative searchterm
Defensive vs Aggressive Rule-Sets
Depending on your strategy, you may want to be more aggressive - for instance to help push the keyword rankings of new products.
This would, for example, mean increasing the bids for Low ACOS keywords earlier, while decreasing the bids of High ACOS keywords after a longer period / more clicks.
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.