Glass is beautiful, but it is also sharp and heavy. Most injuries in the trade occur when handling glass that breaks or slips. Good professional work is therefore always safe work too.
Your body is your most important tool and glass does not forgive mistakes. Always use the right safety equipment regardless of how small the task is.
Much glass work takes place on ladders, scaffolding or lifts at facades and large windows. Handling heavy glass at height requires extra care. Ensure a safe underlay, use fall protection where required, and cordon off the area below you so no one is hit by a piece of fallen glass.
A glass job that looks nice today but is leaky in a year is not good craftsmanship. Quality in the trade is about the pane being correctly positioned, sealed and lasting many years.
Finally quality is also about honesty. If a pane cannot be repaired, say so. A customer remembers a glazier who gave honest advice far better than one who made a quick and poor repair.