On cruise and light throttle i put in enough advance so that the engine feels sprightly but not over advanced (kangarooing) and in boost as mentioned above a few degrees retarded from the point of det. det will not kill your engine if you are carefull when tuning.
Just bought a KS3 knock device with knock sensor, this has been very usefull when mapping my subaru on boost, Just last night it came up with a det warning, only after did i think i may of heard something (6000 rpm very difficult to hear) i then retarded the ig timing by 3 degrees and it has not alarmed since and the car is now quicker.