If you want to become big again after splitting your cell quicker than waiting for them to absorb each other, why not try finding a wall and corner to eject mass towards for one of your cells to eat. This is a strategy used by many players. you can do this without a wall when in 3+ pieces, just feed the piece you want to feed but aiming at one of your small pieces.
It's generally a good idea to eject one mass into a cell (player) much larger than you. They won't bother eating you If you're too small and since you gave them mass they will either team with you or won't attack you. Ejecting to a skilled player and avoid dangers, but watch out for solo players as they generally think that mass shooting means that you're a teamer.
if a bunch of big cells surround you when you're small, be as unpredictable as possible so they can't split TWICE to eat you. (if they split twice another cell and kill him by splitting once)
When you are sure that you are teaming with another player let them eat your smaller cell if you somehow split from a virus, and eat their smaller cell if they split from it.
Even though a bunch of small cells may seem like an easy target, be careful, because it can merge into a cell bigger than you (especially if there is one big cell). If there is more than 6 or 7, do not try and eat that player unless if you can split and eat them.
Use viruses to your advantage by hiding behind them (not in them if you are big) to block another player from eating you. They don't want to split, so they will not pursue you, just make sure that you do not split.
If a big cell is chasing you, find a virus and make them think you would shoot them and they will leave you alone.
You can't always trust the players with names like "u help=i help" and "team?", especially if they already have a teammate.
When getting chased by a bigger cell, they may attempt to split and eat you up. Try and circling around the bigger cell so that it will be harder for them to catch you.
Be careful when teaming in Party. when you split, your teammate might betray you and eat all of you, resulting in a game over. These cells are called Fake Teamers, and you can name yourself #StopFakeTeams for better safety.
If you have 400 mass or more, you can eat viruses. Make sure you are in a place where there is no people and a lot of viruses. split on 1 of the viruses and then use your other piece to scoop up the rest of the viruses.
when massively big (7000+ mass) play more aggressive. splitting twice (into 4) at this stage is the same as splitting once at lower ranks (1000- mass) and don't get worried to split 3 times (8 pieces) if you're sure #2 or #3 is far enough.
if number 2 or 3 is close enough and you're in a million pieces (splitting into 10+ pieces or hitting a virus) aim your cursor at the middle and repeatedly hit W key. this will make your center piece(s) grow bigger and the rest shrink off so #2 or #3 will get scared and not want to stalk you anymore. this "self feeding" tactic is available as long as you have 3+ pieces, just aim your cursor at the blob you want to grow and rapidly hit W key.
Doing so can help get people that you can't engulf after splitting twice eaten.
If using Windows 10, try turning off the mouse precision setting. Control panel, mouse, mouse properties tab, un-check the box for "Enhance pointer precision". If checked, that setting seems to make the cursor want to stick to your cell. The cell is more maneuverable if that box is not checked. In that same spot, you can set your mouse speed to fast, and little mouse movements will have you zooming around.
If using a PC, make the setting adjustments suggested above, then set your browser to full screen -- more space to see danger and the browser seems more responsive.
If you have a wide screen monitor, travel your cell left and right, not up and down. That gives you lots more time to see threats.
If using a PC, the Agario start screen has a resolution setting. For me, there is no difference in the cell appearance if I select low resolution, and the cell is more responsive.
PROTIP 101: You can split to shoot a virus at someone. they most likely won't see you coming, and if you have a small piece and someone overlaps you, lead your small piece to a virus and shoot the overlapping enemy. make sure you don't shoot yourself by being a little farther to the virus than your enemy.
PROTIP 102: If you spot a team and you're playing solo, stalk them until they make a mistake that allows you to separate them. then, use your skills to defeat the bigger teammate. However, be careful NOT to do this to teams 2+ times your mass.
PROTIP 103: If someone overlaps you and you're in 2+ pieces, stay on top of them until you merge. BUT, be careful not to merge a piece that is too small right ON your opponent, instead, use your big piece and watch their movements, then the small piece will gradually come near and merge. this can kill big opponents and especially nasty teamers.
PROTIP 104: if someone viruses you, use your small pieces to bait other players to you and kill them.
PROTIP 105: play aggressively when you're big (10k+) but don't get too aggressive; hitting 2-3 viruses and self feeding can activate the Anti Team Penalty, which will cause you to lose over half of your mass in a few minutes.