There are a lot of ways to use it. Use it on campers. Always launch 2 unless you are sure they are not moving and are in the open. Operation locker has a choke point where people fight outside hiding behind corners. Use mortars n u will probably get like 3 or 5 on the multi kill from people huddled up. So That's One Way. Long range
U can also use it short range as LIke a backup support weapon. When I see like 5 enemies closing in on me I hide in a bush and launch. U can take some out or at least scatter them. In the confusion they will be shot by the squad or get shot by you getting to close to your bush. Once u run out u go back on the attack. You can also attack the enemy with your mortar behind you and strike enemies hiding behind cover.
If people are camping in a house or building. I mortar that and get them out. Sometimes going through the roof for the kill. I don't use mortars on deathmatch. That's klidz. Sr2 does better work.
Conquest, obliteration and domination are the bes the best mortar modes because of all the campers.
After your first hundred mortar kills you should evolve to the next level which are predictive mortar strikes. You can drop a mortar on someone by predicting the path you think they will takr. Yesterday someone was in a jeep with the ball in obliteration and based on the speed I dripped mortars on his jeep and disabled it allowing my team to swoop in and pick his bones.