You want to make sure your teammates know what you are planning and are also in a good position to follow up when you get initiated.
I think baiting your opponents with Sona is very risky as her ultimate and abilities are very helpful to the team and she is incredibly squishy so she could be killed before your team could engage and punish the enemy team. I think it would instead be better to use a more tanky champion that can also hold them in-place or stun them (Rammus and Jarvan), or a champion that has escapes/can disengage (Akali and Kassadin).
As to how to bait the enemy team into falling for the trap, that is very tricky. You need to make the other team think that you are alone. One way of doing this would be for the bait to stand in an enemy team's ward while their allies don't stand in visibility of the ward.
If for whatever reason the enemy team looks too strong or you don't think you can take them in the fight let the person being the bait die and disengage. It is much better to only have 1 person die than the entire team.
There are also some Champions that have abilities relating to death that can enhance your plays, here are some examples:
Karthus: He can cast spells for 7 seconds after being killed thanks to his Death Defied passive.
Kayle: Her ultimate makes a champion immune to damage (2/2.5/3 seconds)
Kog'Maw: Moves faster and blows up after 4 seconds dealing 100 + (24 x lvl) true damage. During the early mor middle game where Kog'Maw isn't fed, it might not be a bad idea to bait with him, but once he starts getting to late game I don't think it would be a good idea to bait him.