I just recently started putting bridges on my beats.
SoundClick artist: Game Productionz - RnB and Hip Hop beats
For me, it just came with time, experience, and using my ear.
What I do is
If im going to put a bridge in my beat, I will use a chord progression that I know is going to transfer smoothly into my bridge. So the last chord in my song chord progression will be that chord that is going to resolve to the first chord in my bridge. Now, if I have a progression that I know is not going to smoothly transfer over, I will substitute a chord in for the 4 chord when the progression loops to the chord before the bridge.
But, whatever my progression is... I know that the 4 chord will lead into the 1 on the bridge. Now when im saying 4 im not talking about 4 as in the scale degree, but 4 as in the number of the chord in the progression.
Its all about knowing where your trying to end up...diminished chords can lead you right into your 1 chord... or a 2 - 5 - 1.