Try your hardest to dodge Vel’koz Q’s in lane. Invest in early Boots if you’re struggling to dodge this ability.
As soon as he channels his Ultimate R, either disengage, CC him or commit to the all-in. Hard CC will interrupt his Ultimate R, but roots do not.
After he has got his first item, Vel’koz will constantly push the minion wave. Stand close but outside of the minion wave at all times so he is unable to push and poke at the same time.
Force team fights as soon as possible: preferably when his Ultimate R is on cooldown. Do not delay a team fight as it will allow him to poke your team down with his Q and W.
Avoid team fighting or forcing objectives like the Baron or Dragon when Vel’koz is alive and nearby. He has great poke thanks to his Q, W and R which will make it difficult for your team to secure the objective easily.
Avoid fighting in chokepoints like inside the jungle as it will give Vel’koz an easier time landing his E, doing damage with his W and melting your team with his Ultimate R.
Vel’koz first major power spike is once he hits level 6 as his Ultimate R offers him tons of kill pressure.
Once Vel’koz has his first item completed, he will be constantly pushing the minion wave and trying to poke you down.
Vel’koz is really good in team fights thanks to the poke and AOE damage from his abilities. Try to fight when he is not there or when his Ultimate R is down.