Albert suggests that like any aspect of playing keyboards is a process. There are a couple of mind-sets, or approaches, you should begin to integrate. First try to play the roots of the chord you are playing with your right hand. One rule of thumb (no pun intended) watch out not to step on the bass players parts. Stay out of his way and don't muddy things up down there! Unless, of course, YOU ARE THE BASS PLAYER TOO. If you are soloing with the right hand, you may be able to play two note chords or dyads with your left hand. The most common voicings to use are fifths, fourths or octaves.
When you begin to feel comfortable with these, try to use the third and seventh on top or the seventh on the bottom with the third on top. You can even try to use these on two different keyboards or a split sound on one keyboard if your keyboard has this option.
Another suggestion while voicing two handed chords is to jump the third of the chord up an octave into the right hand while the left hand plays the root and fifth. Or the reverse where the right plays the root and fifth while you drop the third down an octave into the left hand. Then when you change chords, try to have as little movement or jumps as possible between chords. This works especially well with strings and horn accompaniments. This is only the beginning though!!
For more tips on playing instrument go to Rock House Method.