approx 90deg (arm to cue) is standard,however there are some applications that your grip may need to be more forward or closer to the joint like shots that require more speed. You begin to lose cue stability if your arm is nearer to the butt cap (more than 90deg, depending on who's point of view).
Length of bridge varies with shots also, you want to experiment with this although majority will agree that shorter bridge is more accurate as the margin of error for the cue to get off its straight path is lessened.
If your body, shoulder, elbow, & the arm are steady, the last thing that you must develop during the stroke is the wrist. Keep it relaxed during the swing without flying away like ringing a bell. It should only move straight backward & forward, & release the cue upon impact to let the cue travel straight & let the tip fall down naturally. If you develop the speed of your wrist's stroke, you won't need to swing the arm much anymore to apply the same power (hence lessening the margin of error of the cue diverting from its straight line during the backswing).
Based on my lessons & experience
Length of bridge varies with shots also, you want to experiment with this although majority will agree that shorter bridge is more accurate as the margin of error for the cue to get off its straight path is lessened.
If your body, shoulder, elbow, & the arm are steady, the last thing that you must develop during the stroke is the wrist. Keep it relaxed during the swing without flying away like ringing a bell. It should only move straight backward & forward, & release the cue upon impact to let the cue travel straight & let the tip fall down naturally. If you develop the speed of your wrist's stroke, you won't need to swing the arm much anymore to apply the same power (hence lessening the margin of error of the cue diverting from its straight line during the backswing).
Based on my lessons & experience