Originally Posted by: bunmiadefisayoHow do i transition from one key the other smoothly?

I did a little post on that over here:
http://www.guitartricks.com/forum/showthread.php?t=19844

The main idea is to decide how much you will prepare for the arrival of the key. To completely prepare requires using effective voice leading by means of using chords that approach the new key (i.e. secondary dominants).

So that if you are in C major but you want to go to E major you would look for ways to outline:

C major -> F# minor (or dominant 7) -> B major (or dom 7) -> E major.

Because the function of those chords is to be a ii - V -I pointing to the new key you want to be in. Regarding the voice leading specifically I did a whole thing on that on my music blog:
http://christopherschlegel.thinkertothinker.com/index.php

Hope this helps. Happy playing.