If you see someone on the other team, but you know you can't kill them, try putting as many shots as possible on them. This makes it easy for your team to sweep in and pick up the kill.
This also applies to if you get caught on the losing side of a shootout IF you can't run away. There's nothing wrong with a tactical retreat, you can always come back and get the upper hand. If you can't escape, start shooting. Keep them controlled shots and try to stay alive, but focus on hitting them as much as possible to help your team mates. At the very least, it gives the shooter a reason to hide for a few seconds.
If you have a mic, call out what you can, even if its as simple as "on me". This lets your team mate know where the enemy is so they can coordinate an attack, or save their lives.