The Basics
Basically you now need to understand your quarry more deeply or thoroughly than ever before, and know everything you possibly can about them. Read all the books, thoroughly, watch them if you can from the surface. If you fancy your chances with the "dils", even go diving to watch them, or find them. Listen to other successful anglers "carefully", and if possible watch them on the water.
Preparation and confidence go a long way to your success. Also understanding the rules of the game and how to enhance your chances of doing well will help a lot. Try to "Percentage fish" as this will put you in the right confidence frame of mind.
Most tournaments are "Time Games" in that they require you to catch a certain amount of a species, and often more than one species, in your allotted time period. What you have to do is catch as many of those limits as you can, and if the competition are good then you need to be able to select "Quality spots" where the fish are a bit bigger than the others.
In other words it becomes a "Run and Gun" game, and expect to burn a bit of fuel.

Preparing and practising.
You need to ensure that you have all the right tackle for the species you will be fishing for, and readily available so that you do not waste time, changing rigs and lines etc.
Make sure that you have enough bait and it is FRESH and good quality, and that you have enough.
Make sure that your hooks are sharp and so on.
Don't forget the landing net and if necessary a gaff.
When you are out "practising" look for various spots and just "Test Fish" them, that means just catch one or two to check the general size, and how they are biting. The more you catch in practice, the less there will be when you get back to that spot. Don't forget you may not be the only person that has found that spot.
Listen to your partners ideas, they may work better than yours and take note of what he does. If he is catching more, or less, fish than you, figure out why and correct it, so you can maximise the catch between you on the day.
Where possible do your practice using "Visual" checking of the size and quantity of fish in the area (Do not forget your Polaroids)
Make sure you note where the snags are and what you could do to avoid losing fish in them.
A pretty good idea is not to talk about your practice sessions until after the event, so you do not give any ideas to your opposition as they will be listening if they are not doing as well as you.

The All Species Scoring System
This is the true "Run and Gun" scenario. You have to catch as many limits of five fish per species as possible in a day or over two days, dependant on the event.
The approach is fairly simple if you look at the basic facts of the scoring system, and use this knowledge to maximise your points.
Firstly accept that the "AVERAGE" fish of any species is the same as any other.
Secondly look to attain the average weight in whatever you target to go for.
Simply :-
2.5Kg Tiger = 1Kg Nilo=750 Gram Mellie=300 Gram Squeaker=2.2Kg Barbel and so on
Thus each average fish = approximately 11 points each.

If you do not get the average weight, then a qualifying fish is worth 4.4 points roughly, it just means that you need to catch more smaller fish than the guy with a few big fish.

Interprovincials
In Interprovincials, you have a two day period to get your various limits, but in International type events, each day is a separate event. and fish are not carried forward.
Basically in both events you should have the same target - 100 points per day. This will always put you in the driving seat, and right near the top of the order.

Target a bit high? So it should be if you think of what you should be capable of. Rather not be satisfied with your performance, than settle on a lower target and achieve it, and be satisfied with a lower performance.
This is just 10 Average fish or about 15 to 18 smaller fish per day.

Always target the easiest fish to catch first, but bear in mind that some species are only best at certain times of the day e.g. Barbel and Tiger are early morning species, and possibly may not be the fastest, so set a time limit for that period of the day.
In general you should be able to get about 10 to 15 fish a day without too much problem on the first day. Those spots should be economically used if you have to fish them again for another day such as in an international. If you do not have to then give them to others in your team that have not caught their limit of those species yet.
Try not to have to go for "Improvements" on your fish, as generally that only improves your score by one or two points, instead of the four or five for at least a qualifier of another species.

Provincial, National Leagues and Internatinals
If you are in the "International type" scenario, then ensure that you have a spot for each species for each day, as you may not be able to use the same spot twice, due to them being fished out or spooked, either by noise or lost fish etc.
If you are fishing in a "Team" environment, share your knowledge with all of the team down to the last detail, and ensure that they understand what you say, and listen carefully to what they have to say, that way you will maximise the teams chances of winning. Do not be greedy and selfish, as that way you jeopardise the teams chances of success.
Thus the basic rules for success in this type of fishing is catch two or three species per day, and catch different ones the next day if possible (For two day events).

Single Species limited quantity (E.g. Tiger Tournament)
Most of these tournaments are run on a straight weight scoring system, but have a limit on how many you can take to the weigh bay to score.
Again there are ways to enhance you scores. Play the percentage game. Look at your projected targets and understand how to get there the easiest.
Assume for example that the qualifying weight is one Kilogram and that you only are allowed to take in twenty fish (Tiger Tournament).
Your target should be to make the top ten at least if not to win the event.
Assume that to make the tenth place on average requires in the region of 100 points.
This means that you need to accumulate about 33 points per day. "What !!" you say "We struggle to make it on the board!!"
Well it isn't really that hard to make it on the board if you have a bit of confidence, good eyes and ears and use a bit of simple mathematics.

What is 33 points from twenty fish ? About 1.5 Kgs each, that's all.
The smaller fish in general are easier to find, and generally to catch, so if you can get twenty "weighers" in the boat you are almost there even if they all weigh around 1.1 to 1.2 Kilograms each.
As soon as you get that done, then go and try and find the bigger ones to make up the shortfall.
Obviously if you already have a spot that provides 2 kilogram fish in those sort of quantities, then start there, but expect it to take a little longer.
The same rules generally apply to any single species event, whatever the limit. Get the limit first, and then look for monsters.