The process requires the 15th fret to be pulled, and a small hole drilled through the fret slot into the air gap in the dovetail joint. The fingerboard extension is then warmed with a heating blanket and gently loosened from the the top with a thin spatula or palette knife. Steam is injected into the hole to soften the glue inside the joint. The neck is removed, the heel is slightly carved back at an angle, the the neck is re-glued into the body at the new correct angle. This improves action, tone, volume and intonation. NEVER let anyone shave the bridge lower to fix your problems, as this is a crude, value destroying technique only to be used on inexpensive instruments!
The best ways to try to avoid this problem is to keep your guitar climatized properly, never letting it dry out in the heating season. (See my article on humidification). Over time medium or heavy strings will also add to the guitar's tendency to compress in on itself, requiring a reset to correct the angle issues.