When making adjustments in the Develop module, you can click within any of the numeric entry areas to set a specific value. Then, use the arrow keys to modify the value (add the Shift key to modify in larger increments). However, if you prefer to make changes using the sliders, click-drag to extend the develop module panel to make finer adjustments. Adding the Option (Mac) Alt (Win) key will allow you to expand it even farther.
Note: this shortcut works with any of the panels in Lightroom.