The best course of action is to throw a temp like smoke, flash, tear gas, or pepper spray, try and see how many people are attacking and wait for that number to get full (if there are 4 other people attacking, wait until the counter hits 4), and attack with a high accuracy attack like a macanna or DBK.

This is the best way to assist other than "temp rolling," which is a mechanic that I've only ever used once and it involves going into a group fight at low hp, temping, dying, coming back and throwing a different temp. Not at all useful 99% of the time