(1.) Go slow enough to get your hits! Regardless of the format of the match or the scoring system used or if it's IPSC or IDPA, ONLY HITS COUNT!
(2.) Use factory ammo! (I learned this a long time ago) Unless you are very careful in your reloading and taper crimp all your rounds, you're probably better off to buy a couple of boxes of fairly hot factory ammo to shoot competitively and save the reloads for practice. (I always liked military-spec in .45 and 9mm. I haven't had my .40 long enough to settle on a "favorite" generic factory load)
(3.) Function test your equipment.
(4.) Clean your gun and lube it before the match.
(5.) Replace your magazine springs every three years or so.