Sniping

The most used way to defend a city both in conquest and in revolt worlds is stacking units in the city like DLU, birremes or both. But this not the best way due to the resources lost and the golding era, where players can have their army back in the same day.
In short way, sniping is defined as a support/attack that arrives right before(-1 second, revolt) or right after(1 after, conquest) the colony CS. Even though that precision isn't regular because of the anti-timer system. In the end, it's like playing with a dice, and the more times you throw it the more chances you'll have to get a "six".

Identifying the CS

Usually the CS is the last attack and the slowest one. But be careful some players may trick you with Atalanta lv20, Improved troop movement, Set Sail, Cartography and Lighthouse  and Helmet of Invisibility. All together they improve 104,5% in the speed! CS becomes slightly faster than fireships.
If you're not online, don't worry, you have to look at the chronological time of the attacks and simulate all of them. And cast wisdom if you're not sure.

The snipe

If you're a premium user:

• Create a plan to the city you want to defend;
• Put all the attacks or suppots with the right time(front snipes with the same time and back snipes with the same time);
• Open your command overview and the planner;
• Drag the command overview to the left and the planner on the right;
• One minute before, let the first attack open;
• When the timer hits 10 seconds before the departure time, attack the target;
• If you're not satisfied with the timing, then cancel the attack as fast as possible and repeat the attack by the planner again.

If you're not a premium user:

• Take a paper and a pencil;
• Simulate all the attack or supports you pretend to do in the targeted city;
• Note all the departure times of the attacks/supports;
• Open as many windows as you need(if the departure time of an attack is too far then you open this window later);
• When the timer hits 10 seconds before the departure time, attack the target;
• If you're not satisfied with the timing, then cancel the attack as fast as possible and repeat the attack.

Front Snipe

The front snipe is a support that always comes before the CS. The ideal scenario would be to support one second before the CS arrives, because they are usually escorted by LS nukes. Just remember, the command overview put the battles in order of departure.
You can use in revolt and conquest worlds.
Example:
Clearing attack(LS): 00:01:00
Clearing attack(LS): 01:01:01
Clearing attack(OLU): 00:01:01
The support must arrive here at 00:01:01
CS attack: 00:01:02
Enemy support 00:01:03

You can also use the front snipe to wipe out the OLU of the enemies.

Back Snipe

The back snipe is an attack that always comes after the CS. The ideal scenario would be to attack one second after the CS arrives, because they are usually supported by birremes and DLU. Just remember, the command overview put the battles in order of departure.
You can use in conquest worlds.
Example:
Clearing attack(LS): 00:01:00
Clearing attack(LS): 01:01:01
Clearing attack(OLU): 00:01:01
CS attack: 00:01:02
The attack must arrive here at 00:01:02
Enemy support 00:01:03

You can also use the back snipe to take down the OLU of the enemies in RR, but the city will be lost. If you feel necessary, you can buff your back snipe, casting a spell. The spell keep working even if the troops are returning.

Sniping from the same city

This is the most difficult one, due to lag mitigation, but here we go.

a) Front snipe

• Open the window of the CS attack;
• Choose a city to support(preferentially your cities and close to you);
• Pick a cronometer;
• Choose the time that you'll send the support. Make sure to choose a pair number;
• Multiple the time calculated by 2;
• When it hits the time of the last attack, then cancel the support.

Example:
Last attack: 0:01:00
CS: 0:01:01
Your support: 00:01:00
In this situation, you have to send the support when the last attack hits 00:02:00 and cancel the support when it hits 00:01:00.

b)Back snipe

• Open the window of the CS attack;
• Choose a city to attack(preferentially your cities and close to you);
• Pick a cronometer;
• Choose the time that you'll send the attack, don't forget to buff it with a spell. Make sure to choose a pair number;
• Multiple the time calculated by 2;
• When it hits the time of the CS attack, then cancel the attack.

Example:
Last attack: 0:00:59
CS: 0:01:00
First support: 00:01:01
Your attack: 0:01:00
In this situation, you have to send the attack when the CS attack hits 00:02:00 and cancel the attack when it hits 00:01:00.

Timing attacks

In order to avoid dodging and birs sniping(front snipe), your attacks must be timed. The gap between the LS nuke and the OLU attack must be the lower possible. A good sniper would land the LS and OLU in the same second, which will counter the birs sniping, then the defender must have more birs sniping to help him.
In conquest worlds, it's crucial to support in the same second of the CS(of course, the support must be send after the CS, then the rule will do the rest), because players can front and back snipe your sieges.

PS: You still need LS in your OLU cities. It doesn't matter how good you are, Sea Storm can easily destroy the CS and if you send a bad escorted OLU, others can snipe spliting their birs in groups of 70/100.

Using anchors

Anchors are single units slower than your troops like: transport ships, fire ships and LS(in birs cities). In the land: swordsmen and catapults
Such precision wouldn't be possible without anchors. With them you have more chances to get a "six" in the dice, because you can try to snipe more times.

Any doubts, post in the comments.