Box out the entire scene. Then take each element into rough detail first, then finer detail after.
Loop cuts are a fast way to add topology but be wary of adding too much to stay in low poly.
Moving vertices around a little randomly and rotating/scaling loop-cuts helps to give character really fast.
Use CTRL
+ P
to parent a selection to the active object (opens the parenting menu).
It's handy to parent a selection of meshes composing an object to an empty to be able to move the empty to place and move the object easily afterwards.
When placing such empties, be wary of the origin point of the empty as snapping to faces afterward will use that empty's origin.