To help prevent leaks and call backs, you'll want to follow correct procedures. Cut tubing with a quality cutter and a sharp wheel for a clean right-angle cut. A sharp wheel will ensure that tubing isn't closed in. To avoid tube constriction, use a light hand in turning in the feed screw. Deburring is necessary to remove the cutting burr.
Unremoved burrs can break off and go into the tubing or scratch the flared surface.
Use a deburring tool or even a stout knife to remove burr. Flaring must be done correctly since over flaring and under flaring will prevent a good seal. Always use an oil drop on the flaring cone and feed screw for smooth, precise action.