As long ago as August 16, Matt Cutts commented:

"expect that the next few Penguin updates will take longer, incorporate additional signals, and as a result will have more noticeable impact."
http://www.seroundtable.com/google-p...ing-15577.html

As yet there has been nothing definite about when we can expect this to happen, but the message is clear that although Google considers the impact of the original Penguin to have been relatively small (compared to Panda) it is going to hit more sites when it is eventually run again.

In the absence of the expected "links disavow" tool (which is the subject of another thread so please do not discuss it here), what can website owners realistically do in advance to try to prepare for what is to come?