If you are adding Rift Lake cichlids to a tank, add them all at the same time so nobody gets a hometown advantage. You should also try to get fish that are the same size so they are more evenly matched.
If you already have cichlids in the tank, rearrange the tank ornaments/ decorations just before releasing the new fish into the aquarium. This helps break up established territories and gives the new fish more chance of finding somewhere safe to live. If you don't break up territories the original fish will consider the newcomers as intruders into their home and probably kill them.