In general anything where you have a big bet out, and are still close to the index, I would be gun shy about making the doubles and splits. Some of the more common situations are:
-Doubling 8 v 5
-Doubling 10 v 10,A
-Doubling 9 v 7
-Splitting 10's v 5,6
-Splitting 88's v 9
Similarly would tend to take a surrender more often at a shade under the index:
-Sur. 14 v 10, 14 v 9, 13 v 10, 15 v 8, 16 v 8, etc.,