Tick anything you already have, in any order. Quests unlock once this is done.
A cheap kettle grill with the coals banked to one side smokes properly. The thermometer is the real requirement, because low and slow is a temperature, not a feeling.
2 things left above. Quests are real things you go and do, so they only make sense once you have what you need.
First one waiting: Hold a steady low temperature for hours