Have at least two plasma grenades when your partner cannot find you. Throw one in any direction and without moving as quickly as possible, throw a second one. The first one will explode, sending the second one flying into the air. The grenade will explode at a very high point, acting as a flare so your partner can see where you are located. Note: Make sure that you do not move in any direction while doing this, or the second grenade will not go into the air, only sideways if anywhere.