I find that rides with lots of seated riding are more liable to set it off on the occasions that I get it; good stretching helps a lot, as does rest. Always try to stretch a bit when we stop for a breather and snack and chat too.
Also, make sure I stay hydrated and fed; more susceptible to pain if the muscles are working and have no fuel to burn - lactic etc I guess; we've all felt it in the legs etc, no reason for it to not affect other muscles groups if you are using them a lot too.
Better having gone to the full sus too; takes some of the jarring out of the ride for sure.
All of these things really just point to not making the back muscles work excessively compared to what they are capable of; sus to take some jarring bumps, getting out of saddle to let arms and legs do more compressive work, keeping them all fuelled to work as well as they can...
Obviously this is relevant only if your bike fit is right for you to start with