It really all depends on the image you are working on and on your "taste" as a photographer and a "digital darkroom" developer.
I myself tend to open images using the Lightroom defaults, then for a set of images I'll eyeball and adjust one "master" image to taste. If all the shots in the set are a lot alike in terms of lighting, exposure, etc, then I might set the Lightroom Develop panel to "Auto Sync" so that when I adjust the first shot the other selected shots will get the same. Otherwise, I can either synchronize a group or not.
But that being said, I'm not much for using Presets, or even for messing around with the Camera Calibration profiles, but those things are there and a lot of people get use out of them.
So, my suggestion is that you take your time, keep "current" with what others are doing, check out the many resources for Camera Raw, and in time you'll develop your own preferences! In time you may find settings that you want to either apply to all your images when you import them, of maybe settings that are specific to a particular type of photo. You can develop your own Presets in that case that you can apply at any time in the process.
One very valuable book to check out is "The Digital Negative" by Jeff Schewe.