Fourth in hand, with shortage in preemptor’s suit, don’t look at the rest of your hand, double!
Discuss the meanings of balancing bids with your partner.
Laziness is one of the seven deadly sins, in bridge, too; laziness loses.
Nine tricks are easier than ten; try bidding 3NT with a major fit sometimes.
If you are inviting, do it the right way.
Don’t get caught speeding, especially after partner may have been stuck for a bid.