Your 624 is not an overly large revolver, but it does have the typical N-frame cylinder in the typical N-frame, so it is not a compact piece by any means, and has a loaded weight of about 2.6 lbs. For discreet and comfortable concealed carry my first recommendation would be a pancake style holster worn just behind the strong-side hip (about 3:30 to 4:00 position for a right-hand shooter), butt-forward cant of about 15 degrees. The pancake-style holsters tend to disguise the bulk of the larger revolvers, particularly the cylinder bulge, and the offset belt loops fore-and-aft keep the holstered revolver pulled snugly into the body while also spreading the weight over a broad area of the belt.
Second recommendation is a sturdy gun belt, which serves as the foundation of the carry rig, anchoring the holster in the desired position and supporting the weight without having to be tightened to an uncomfortable degree. Many unfavorable experiences with holsters are actually failures due to a belt that is not capable of performing the job, especially with the heavier handguns.
Best regards.