In my opinion, default settings are whatever looks right to you and your type of shooting. This isn't something that someone else can recommend for you. Take some pictures and evaluate the settings that you have to make. You will begin to see a pattern, and then you can decide what settings should be the default. If that changes then you can always change your default settings.
Really, this is a question you should be asking yourself...
What do you shoot? Makes a difference...
Typical ISO that you shoot? Makes a difference...
Shooting for clients or yourself? Makes a difference...
Look, there is no magic bullet...the ACR/LR "Default" should only be changed for those adjustments you make 70-90% of the time and sould not be confused with image by image adjustments...
So, as asked, your question can not really be answered other than to say, use a default that suits you.
What Jim and Jeff say. One shoots raw and uses ACR because one wants absolute control over everything. There is no such things as rules here.
Thank you for your responses. I realize that there are no hard and fast rules and that it depends on the actual shot. I was just wondering if there was an amount for e.g. of clarity, saturation or vibrance etc that anyone had found was something to begin from. For e.g. with my OLD 20D I always needed at least 10 for saturation etc.
But thanks anyway.
You might want to experiment with Camera Profiles, but, other than that, my advice is the same: if you use some settings most of the time, make them default.