When beginning to play the guitar, many players are in a huge hurry to master the fret burning licks on their favorite recordings. At the early stages of learning to play the guitar it is important to walk and master the basics first.
I found a cool little video on You Tube that talks about how to properly position your fingers on the guitar strings to obtain the proper sound, and not have a dead dull sound.
There are occasions when you would want to put your finger directly on the fret to obtain a "harmonic" note. This will be covered in a later lesson.
The basic idea is that each fret on the fretboard, shortens the length of the guitar string to produce the note you are looking to.
Check out the video lesson for a bit more of a description.