Matches played as Killjoy
Both [E] Turret and [Q] Alarm Bot are both incredibly effective tools that you need to play around throughout the round. For this reason, consider how you want to play throughout the round before placing them, so that you are able to move freely through the map without de-activating them until needed.
[X] Lockdown is such a powerful site execute and retake ability, that enemy players will often save abilities like Sova's ultimate [X] Hunter's Fury to destroy it.
Typically, you should place [E] Turret in positions that alert you to an enemy player's presence in a certain area of the map, or that disrupt enemy players trying to move through a certain area of the map.
[C] Nanoswarm is very effective in post plant situations. Just throw it either off to the side of the spike where enemies are unlikely to destroy it, or throw it directly inside of the spike, and then activate it from a safe position that allows you and your team enough control of the Spike.