First things first.....casting a baitcaster is NOTHING like casting a spinning reel.
Next, before you do anything, rig your bait up (ex. senko t-rigged). Then hold your rod tip at 10 'o clock in front of you. Tighten your cast control knob all the way. Hit the clutch. The lure should not move one bit. Then, slowly, un-tighten the cast control knob until the lure falls slowly to the ground.
Now you're set to cast. Practice casting overhead first. If you have a RH reel, make sure the knobs and handle are facing up. Hit the clutch, hold your thumb firmly on the spool, move your rod tip back behind you to ten o' clock and load the rod tip up w/ the weight of your lure, then fling your rod tip to about 11-10 o'clock in front of you then let go of the spool w/ your thumb. Don't touch the spool with your thumb until the lure is about to hit the water, lightly put pressure on the spool just as it hits the water. Reel the lure back to you and repeat until you get the hang of it. Make sure that your reel handle is facing UP throughout the entire cast. Later on, when you get the hang of it, you can cast any which way you please.
Hope that helped. Trust me, all the practice WILL BE WORTH IT IN THE END.