As a melee champion, do not go for extended trades with Fizz as he will always come out ahead thanks to Sheen and his .
Unless you benefit from any other wave manipulation, try and keep the wave even or closer to your side. This prevents him from engaging on you or chasing you down.
Fizz has insane roaming potential. Do not blindly follow him as he can easily turn around and kill you. Instead, communicate with your team follow him from a distance if possible.
When walking the rift, do not go alone. Fizz can easily assassinate somebody who is walking through the river alone. Take appropriate paths through warded areas whenever possible.
Do not use any executing s or abilities on Fizz unless he has already used his as he can easily dodge them by going untargetable.
Fizz sometimes relies on his to deal as much AO damage as possible. If you’re caught out of it and near your allies- do not walk close to them as it will deal damage to them as well. Ideally, dodge the ability if possible.
Keep an eye on your XP bar between 5 and 6. If you look to be hitting 6 last, back away and play safer. Once Fizz hits level 6, he will look to all in you. Do not give him the ability to by playing safer until you’re also 6.
Once Fizz has his Sheen (from Lichbane) his damage output will be insane. Do not go for extended trades unless you can fight back because he will always come out ahead.
Fizzes’ Playful / Trickster allows him to dodge damage and escape ganks. Do not go for all ins unless he has already used this ability beforehand so you’re guaranteed to hit your abilities on him.