Like you, I have a Sherwood Wisdom 2 (which will handle Nitrox or Air).
I set mine as follows:
Wet activation = on. In case I forget to turn it on. However, you have to turn it on to check your air before a dive, and I have to turn it on to take an altitude reading before I dive here at home...
Ascent = on. This alarm goes off way too often, but not because I am ascending too fast. Usually it is because I change position or pull my computer up to look at it, or both at the same time. Nevertheless, I leave it on in case I might be ascending unknowingly in poor visibility conditions.
PO2 value = 1.4 This is for when you dive with enriched air (Nitrox). If you set it at 1.4, the W2 will actually alert you at 1.2 that you are approaching your maximum oxygen exposure limit. No depth is actually entered into the computer, although depth is a factor that the computer takes into account.
FO2 Default = OFF. When using Nitrox, this setting will automatically set your FO2 to 50 if you forget to enter a value before a dive. I turned this off because I nearly always use the same mixture, and it isn't 50%. With it off, it will stay at the last value that I entered.
Max Depth Alarm = 100 ft. I don't typically dive this deep on purpose, so I have it set to let me know if I am straying below where I usually want to be.
Turn pressure = 1000-1500psi. I check my air frequently, so I use this mostly as a reminder that I really need to be sure I am paying attention and not starting off on some new path.
End pressure = 500 The Wisdom 2 will calculate your air consumption and will show you the gas time you have left. It automatically figures in how long it should take you to ascend at a safe rate AND make a 3 min safety stop. When you reach the surface, you should have 500 psi left in your tank. You could set it lower, say 300, but gauges can be wrong. I like the safety margin.
Reserve Time = 5 min. This alarm lets you know when you have 5 safe minutes left (or whatever value you have entered) based upon whichever factor (nitrogen, O2, or psi) is most limiting at the moment.
Deco Alarm = on. Since I am strictly a recreational diver, I hope this never goes off.
Sample rate = 15 sec The W2 takes readings internally many times per second, but this is the rate that it will collect data to download to your desktop computer. The faster the sampling rate, the fewer the number of dives you can keep in memory for download later. 15 sec = 15 hours of collection. 30 sec = 30 hours. Sometimes I set mine to 30 if I am going to be making lots of dives (such as a whole week of diving) before I will have the chance to download the information.
All the above said, I must also say that even though I have all these alarms set, I have a hard time hearing them, especially if I am wearing a hood. It is usually easier to hear my buddies' alarms (which makes me look to see if it is mine that is going off).
Hope that helps.