Any BG: place your circle where the buffs (speed/heal/enrage) spawn.
WSG: Take flag, port up to the second floor. Attackers in the flag room will have a harder time catching up.
Any BG or Arena: Place circle on high ground and jump to a lower tier to join the battle. Nuke/DoT until you take some heat, then retreat to the higher tier. The inverse also works, but not as well, as attackers can jump down to get to you. Examples: bridge in Blade's Edge Arena, towers in AV, graveyard/base in WSG, lower ramp around the EotS flag spawn, below the path leading to Dun Baldar in AV. Behind walls or on the gun turrent perches in SotA/Wintergrasp.
EotS: Fighting tends to be heaviest at the flag and at the base you are heading to. Leave your circle just out of the fighting zone at the flag spawn or at the flag return to avoid trouble.
Any BG: Teleport inside of buildings to confuse your enemy.
AB: Teleport underwater when you want to GTFO. Probably easiest to set up when defending. Putting your circle on top of the Mine roof is an especially effective escape, and put it near the edge at Lumber Mill to avoid getting knocked off.
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I don't think it would be smart to teleport somewhere to drop your poison during Grobbulus, as you don't really know where it would be best to drop it when you set your circle. It would be more effective to run to a corner to drop your poison and teleport back to continue DPSing.
Four Horseman: Demonic Circle where the chest spawns to ninja your badge before everyone gets there and takes forever
