Dear Dominion Players (that doesn't mean you die hard Summoner's Rift fanatics, some people like to play more then one map, deal with it.) Here are a set of rules that you should read and follow for the sake of victory.
Rule Number One - After a fight for a point and you're going to recall back, for all that is righteous, do not take the health shrine. Seriously, you're recalling, you don't need it. Leave it for someone who isn't going back and needs the health to hold the point. I cannot fathom the stupidity of getting the health shrine if you're just going to recall. If the point is attacked while you're still there, then grab the shrine and fight.
Rule Number Two - Do not hesitate. The more you try to run, the less damage you're doing. When you commit, either you die or the enemy dies, no retreat and no surrender. The moment you hesitate, the greater chance the point is going to be captured by the enemy. Death does not matter, what matters is the capture, victory at all costs.
Rule Number Three - Stay on the point. You know how in Summoner's Rift that towers are pretty damn deadly? They can also be fierce in Dominion and help protect you against two other opponents. Defend the point and do not be baited out of it. The only time this is acceptable is when your other point are being contested and no one is there to defend it or when the entire team is coming your way; no point dying for a hopeless cause; regroup.
Rule Number Four - Control your blood lust. Chasing after the enemy will only land you into a gank and make your point vulnerable for enemy capture. Ganks are for the sole purpose of dealing with the enemy outside of their turret to avoid being pounded by the turret. Unless you don't have the point nearby, don't chase; the turret is your friend, unless it is red. (Fully aware of the colorblind, but I've never used color blind mode to see what turrets are like when captured by the enemy team.)
Rule Number Five - Cooldowns are the enemy. The longer you're running around with your thumb up your butt waiting for your spells to get off cooldown, the more time the enemy gets to kill you. If your champion has long cooldowns, get cooldown reduction. As a mage, early on Ionian Boots will be your best friend. Burst damage is also quite useless, as you may kill one, but you need to deal with many. If you're a burst damage character, go to bottom lane.
Rule Number Six - Mobility is key. Characters like Xin Shao and Jax are pretty popular in Dominion, as they are bruisers with gap closers. As League of Legends suffers more from the mobility creep, it is crucial you have an escape plan or some decent crowd control.
Rule Number Seven - Crowd Control is essential. Some team wreckers can only be stopped by crowd control, the harder the crowd control, the better. Hard Crowd Control consists of knock-ups, position changers, and other effects that can't be countered by Tenacity. Alistar is infamous for his hard crowd control, this is why he's a common ban. Mercury's Treads help against regular crowd control, but not at all against the hard stuff.
Rule Number Eight - Capturing Points wins the game, not killing the enemy. If the enemy team fled, capture the point. The only time its acceptable to chase and kill them is if they can harass you and stop the capture of the point. The three points you want to keep at all costs are the top, your team's middle, and your team's bottom (lol). Unless you're dominating at Dominion, taking anything beyond those three points will spread you too thin and make your team vulnerable. The enemy bottom and middle are harder to defend since the enemy spawning area is closer, this should be obvious.
Rule Number Nine - Supporting is Tanking. A tanky support is a lot more useful then a squishy ones, all the rules apply to them. Cooldown Reduction, Crowd Control, and Tankilicious are what make or breaks a support in Dominion. This is why Soraka doesn't do well without tankiness, the enemy team will target her to get rid of those heals.
Rule Number Ten - Remember the healing reduction. All healing in Dominion is debuffed by twenty percent, so potions and healing abilities are reduced, even health shrines suffer from this reduction...I'm pretty sure...Champions who rely on healing have to remember this. A good way to counter the healing reduction is Spirit Visage and Spell Vampirism. As a side note having trouble with Life Steal? Executioner's and Morello's Evil Tome will help greatly in the fight against healing, remember this when fighting champions like Jax and Akali who utilize both Life Steal and Spell Vampirism.
Rule Number Eleven - Attack Speed. As I said before, champions like Jax and Xin Shao are pretty popular in Dominion, Teemo as well being the most popular according to LoL King. A great way to counter these auto-attackers is Attack Speed Reduction. Champions like Willump (Nunu) and Malphite have built in Attack Speed Reduction. The items Frozen Heart and Randuin's Omen as well help reduce attack speed. An early Warden's Mail will go far. On the other side, champions that naturally increase attack speed for their allies are pretty useful, such as Nidalee, Willump, and Warwick. Attack Damage Debuffs are also pretty handy, champions like Tryndamere and Urgot can do this. I would put Trundle, but his Q's debuff is rather laughable late game. Don't underestimate Ninja Tabi, that 10% auto attack debuff is no joke.
Rule Number Twelve - Build to Counter. If one particular enemy is carrying their team, build to counter them specifically, without the head, the body runs around for several minutes looking like an idiot. Prioritize. The damage dealers go down first. The exception to the rule is Darius. If he get his face rolling on the keyboard, take him out before he can start spamming his ultimate. Kite him if possible, his pull is somewhat unreliable. Jayce is as well hard to counter since his percentage damage is magic damage instead of physical damage. Yorick is tricky, but if you can commit to killing and escape his angry ghost, job well done. Don't bother trying to kill Yorick or one of his allies if they're brought back as a not so friendly ghost; its wasted effort, they're already dead.