Tips & Tricks #3 on Agar.io
#1 Avoid getting eaten!
If somebody is heading right at you for 3 seconds without swerving, expect them to fire. If you're a good player, you should be able just to snipe them without regret. What you can do to avoid getting eaten, is try to make it as awkward as possible for them. They're not going to fire at you when you're at a 30-degree angle, or whatever is hardest. This primarily works when they are doubled. Usually, this works, because most people are noobs with noob aiming mode. Adopt a habit of skittishness in Agar.io. Make it a policy of running from all players on screen.
#2 Don't hesitate to eat!
One of the biggest mistakes people make in Agar.io is hesitating. They wait for the perfect opportunity. A good player can snipe people without hesitation. How? Don't calculate. Remember one rule here: "If it looks like you can, you can. If it looks like you can't, you can't." Keep that rule in focus, and avoid calculations at all costs. As you play more, your ability to calculate will become perfect. Your greatest chance to eat somebody in Agar.io is within the first few milliseconds of the encounter when they're still on a collision course with your character. Remember that rule, and you're golden. Don't be afraid! Practice aiming at low levels to get good at this.
#3 Focus on the enemies!
I tried both strategies, cell eating, and dot eating. However, dots eating is painfully slow in comparison. You're not a gatherer, and you're a hunter! Don't be afraid to take a little loss over a few cells, because doing so will make it, so you're more focused, faster runner, far more difficult to eat. When people see you're not going for the dots, they can't predict your movement! They lose interest very quickly. A stronger player who can eat more people and find better opportunities, then suddenly will appear in the leaderboard. Secondly, go try playing team mode for about an hour. After going through this torture for an hour you'll see that you simply can't focus on the dots, and you have to run from everybody! If you take this mentality to FFA mode, you'll dominate.
#4 Eject a small amount of mass!
Trying to lure an enemy by ejecting some mass into their direction can be a surprisingly effective way of fooling them into getting eaten. This works especially well in Teams Mode when you have your allies as a backup. Only eject a small amount of mass towards a cell significantly smaller than 1/2 your mass. If they come towards you to take it, split to get them. If they don't, eject more mass. If they still don't take it, eject some more mass and split towards them. You will be using your ejected mass as a mass booster for splitting. When you split it, half of your main cell will almost instantly absorb the ejected mass while boosting you forward a significant amount towards the cell you want to eat. Now you can split again to eat that cell.
#5 Mind trick your targets!
One method you can use to catch cells easily is to fake playing passively. Often you'll find smaller cells zooming around your cell or dodging your cells split attack when you telegraph your intent to split towards them. You can trick them by simply going in another direction and as they get near, instantly turn your direction and split towards them. If your aim is accurate, you can catch someone off guard with a very easy split attack as they will not expect or be able to dodge your sudden movement. This trick can work at all levels of mass, but is best executed by cells with a mass less than 1000, due to bigger cells having slower instantaneous movement. Often larger cells cannot dodge cell attacks due to slower movement.