Side missions in inFAMOUS: Second Son are simple tasks such as locating security cameras or disrupting activist rallies. There aren't many in the game, but all can be found below. Many of them reward players with trophies.
Disrupt 10 activist rallies.
Akuran Gang Members
Kill 10 Akuran gang members.
Rescue 10 escaped conduits from angry mobs.
Complete all district showdowns (complete other side activities/missions to unlock district showdowns)
Take out drug dealers; bust 10 for the "Just Say No" trophy.
DUP Security Cameras
Destroy all DUP security cameras.
Find the 15 hidden cameras (found in separate missions) and shoot them. You have to use your phone to locate the hidden cameras.
Find the Secret Agent in each area of Seattle. Chase them down quickly or else you'll have to restart the mission. Careful if you shoot them from far away - missing means they might get away.
Shoot 10 sign twirlers.
Find the 29 stencil art locations and get to painting. Players have the choice of good or bad karma creations.
Attack 10 street musicians.
Rescue 10 suspects from suspicion pens.