There are several ways to copy and past settings from one image to another in the Develop module:
• Command + C (Mac) | Control + C (Win) will display the “Copy Settings” dialog so that you can choose what setting to copy.
• Command + V (Mac) | Control + V (Win) will paste those settings.
• Command + Option + V (Mac) | Control + Alt + V (Win) will paste all the settings from the previously altered photo.
• Command + Shift + S (Mac) | Control + Shift + S (Win) will display the Synchronize Settings dialog box so that you can choose what settings to synchronize ( you must have multiple images selected to use this shortcut).
• Command + Option + S (Mac) | Control + Alt + S (Win) will synchronize multiple photos with the last copied settings – without displaying the sync dialog box.
• Command + Shift + R (Mac) | Control + Shift + R (Win) will reset all settings applied to an image.
• Command + Option + Shift + A (Mac) | Control + Alt + Shift + A (Win) will toggle Auto Sync on and off in the Develop module (note: you must have multiple images selected to use Auto Sync.)

I believe the first two shortcuts above require the addition of “Shift” in order to work in Lightroom Develop module…
Thanks for the note Howard. I’m using LR 3.6 and I just double checked (because we all know I’ve been wrong before!!!). I can copy and paste with out having to use the Shift key in the Develop Module, but you raise a great point, you do have to add the Shift key if you want to copy and paste settings in the Library Module.