Задать общий, к подлежащему, альтернативный и разделительный вопросы:
1) They seldom complain
2) He will fly his private plane to Florida.
3) The pirates were digging for the hidden treasure.
4) The camels are spitting at the tourists

К каждому нужно все задать

Do they complain?Who will fly to Florida?Were pirates digging for the hidden treasure or for plant a tree?The camels are spitting at the tourists,aren’t they?