[Saphire]

Geoff the best settings I have mine set on with the 170-500. are the following.

First of all try and shoot in RAW then if you do make a mistake with the setting all may not be lost you may be able to correct things in a good editing package.

1. AV. Always have it on this except when I want to experiment with manual.
2. ISO basically depend on the light 100-400 for normal light. In extreme conditions like the weather the way it is at the moment 800 and even 1600.
3. Compensation I usually have in two modes if I know I am going to take flight shots with light background I give between +1 to 1.1/2. for birds on feeders and with plain backgrounds like grass -1 on a dull day. just to bring out the shadows a bit. I have gotten so used to where the compensation switch is now its second nature to change quickly from one to the other if the need arises.
4. Speed. I know they say to keep the speed to whatever length you have the lens e.g.. 400mm. speed 400. I have found what is comfortable for me to hold the lens with no shake sometimes half that amount or less I can hand hold at 450mm down to 125th.

Play around with those setting and get used to where the compensation button is so you are always at the ready. I just played for a while and kept checking the histogram to find the best settings.
Enjoy your camera and just keep playing. When you get more adventurous try the manual setting but don't forget to switch it back to AV afterwards.