Blimey, something I agree with
Constant grip pressure is extremely important in cue sports. A lot of misses are down to people increasing the grip pressure as they move closer to the CB and this ends with the tip not contacting where they intended. Its more common on hard shots, people tend to have an iron grip on the cue when playing with power.
Also the firmer grip is good advice. How do you define firm? Its hard so its best not to go into it. If you cradle the cue, and don't have it touching the webbing between thumb and index finger then its quite difficult not to have a loose grip...and also the change in grip pressure has a more drastic effect on the contact point on the cue ball. I would advise anyone struggling with a cradle like grip to wrap the fingers around the cue and have the webbing in contact with the cue at all times.