Hi Everybody -
There are some benefits to starting with Camera Raw, if you are familiar with how it works. If not familiar, the best advice is to stay away or practice with other pictures first!
If you are familiar with camera raw, using Photoshop CS5 it is a wondeful tool. You can open a JPEG in camera raw (which at first might seem backwards if you didn't capture the image in RAW format). But there are lots of useful features there that you can use to prepare the photo for touch-up.
Most noteable is luminous noise reduction.
All cameras, including the ones used to photograph images of images, produce noise.
In addition to that, many photos you'll retouch have noise in them (either from high ISO, poor optics, low light, damage, etc.).
For me, cloning and healing is easier if the image has less noise from the start. It also tends to soften skin tones on photos taken with disposable cameras or high ISO film (that speckle look).
Camera Raw for CS5 does this beautifully.
The default settings for Camera Raw are a different resolution in ppi, but they shouldn't affect the image quality. This is only the print resolution of the file.
If when you open camera raw you click on the hyperlink below your photo (pictured below)
...you can change the desired color space and resolution back to "Adobe RGB" and "300dpi"
once in Photoshop you can confirm this in Image > Image Size if you want to double check.
If you forgot to click the hyperlink in Camera Raw, in Photoshop you can just go to Image > Image Size, make sure "resample image" in unchecked, then replace "240" with "300" and the length and width will change back to the originals.
Save your result image and off you go!