Learn to Press "Lock in"

Yes and no. Only if everyone's decided on lanes/comp. Then you should lock in. Insta-locking on the other hand, is one of the worst things you can do from a team comp perspective. You want to avoid going too heavily AD/AP and you also want a balance of damage and tankiness. Sometimes the few extra seconds can make all the difference.

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1768609009/47383026?tab=overview

this is what happens when people instalock. they took 5AD in a ranked game, they had a crazy gold lead, then our armor caught up and we wound up winning every teamfight with maybe losing one person.

(The kalista left as soon as we all bought a little armor.)