There are many factors to consider when setting up a potential dive in League of Legends. I am going to try to go over as many of them as possible so you will have all the tools necessary to accomplish a successful dive. First off it is important to recognize the situation for where a dive is possible. This is a checklist to go over before you attempt any dive. After some time, it will become second nature, but it is helpful to deliberately go through each step before you have it down.

Checklist

Am I (we) stronger than the enemy Laner(s)? Look for things like level advantages or item spikes. Sometimes something as simple as a health advantage is enough.
Do I have more cooldowns available than them? Think about ultimates, summoner spells, or even longer cooldown basic abilities like Sett's W.
Are they an extremely difficult champion to dive (e.g. Thresh, Sett, Fizz)? Champions like this are extremely difficult to dive because they can either be extremely tanky, have massive amounts of crowd control, or can just avoid damage to stall the dive.
Where is my Jungler and other roaming Laners? Call allies to help execute the dive, the more the better.
Where is the opponent Jungler and other roaming Laners? This is really important to make sure that your dive doesn’t turn into an ambush. Play it safe and if you think the enemy Jungler could be botside or the enemy Mid Laner is missing, just don’t dive.

As you can see here this seems to be a fairly good dive set up. You have a cannon wave which is great, and a nice two versus one from both sides leaving no escape.

This would be a really bad dive because as soon as either team member enters the turret range you will take the aggro. And the enemy can easily run away from the turret since you cannot corner them.

After working through this checklist and you have determined you are stronger, you have more cooldowns available, your Jungler is nearby and able to help you in your dive, and the enemy does not have any reinforcements coming, it is time to set up the dive. First and foremost, push the wave. Like really hard. Make sure you lose as few minions as possible so you are able to have as much time before commencing your dive. After your wave is shoved in, it is important to call some additional help. Whether that is your Mid Laner, Jungler, or just a 2v1 in the Bot Lane, you want all of the odds to be in your favor for a dive in Solo Queue. After you have some help, and you are positive no other help is coming for your opponents, it's time to start the dive. Diving is all about being able to deal enough damage while avoiding as much as possible from the turret.

Juggling Turret Damage

Since turrets ramp up in damage per shot on the same target, it is very important to juggle aggro (swap targets). To do this, you should have the first person to tank the turret be either your tankiest member, or someone who can easily get out of the turret range or have some other way to drop turret aggro, for example Fizz’s ability Playful Trickster. In that situation, Fizz needs to land the first hit on the target so that they are targeted by the turret first. Then after taking either 2 or 3 turret shots depending on their health, they should use their E in order to switch the turret aggro to another member. This is typically when dives fall apart. It is fairly rare/difficult to kill the enemy player within just a couple of turret shots so it is very important to juggle the aggro correctly. After whoever tanks the turret first leaves aggro, the next person should only be prepared to tank one to two hits before subsequently also leaving the turret range.

Play It Safe

The dive usually fails right after the first or second turret aggro switch as after your team kills the enemy, you tank one too many hits and die. To avoid this, always play it on the safe side. You can always go back, but a one for one in a dive is worth it for the divee as they weren’t the ones investing the resources into it, they were just merely trying to survive. To be honest, it is very difficult to pull this play off in Solo Queue if you are similar power level to the enemy unless you meticulously check everything off the list. With that said dives are a great way to get ahead in a game and further pushes your advantage. The consequences of a successful dive leaves the enemy missing a lot of farm, and you with turret and kill gold.

What to Do After a Successful Dive

This part is relatively self explanatory, but it is still important to try to optimize your lead as much as possible. If the dive went perfectly and everyone lived, just try to press your advantage by trying to take the turret to collect plate gold and so that your opponents lose as much farm as possible. If it is pretty early and you don’t do that much turret damage, it might be better to take an objective like Dragon or Rift Herald. The loss of farm and experience is potentially even more detrimental than the difference in gold from their death.

How to Salvage a Broken Dive

This is the trickiest thing to do. Once a dive starts to go wrong it becomes very difficult to bring back. Sometimes the best thing you can do is to abandon the dive. Do not get yourself killed because your ally is going to die. Your opponent getting 300 gold is better than 600 gold. Other times though, it is better to try to fight through it if you think you can pick up a kill or to stall long enough for back up.

Summary

Dives come down to perfect execution and set up. Any little mistake can easily mess up everything. To prevent this, be meticulous about the set up and be judicious about when you choose to dive. Instead of looking for reasons to dive, look for reasons not to. If there aren’t any, you are clear to dive. In solo-queue, this is the hardest type of play to make so you really only need to do it if you are 100% positive it will work. Always dive with a purpose. As silly as it sounds, don’t dive because you have nothing else to do. Dive because you know it is the best thing to do at that moment.