The horizon is your eye level
The horizon represents the viewer’s eye level in a level scene. Raise it and you tend to see more top surfaces; lower it and you may see underneath objects. Place it deliberately before adding boxes.
One point: face the box
In a simple one-point view, the front face stays rectangular and edges receding straight away converge towards one vanishing point on the horizon. Draw a rectangle, connect its corners to that point and choose a depth along those guides.
Two points: turn the box
Turn a box so its front corner faces you. The two sets of horizontal edges recede towards different points on the horizon. Keep verticals vertical in a conventional level two-point drawing. Widely spaced points usually avoid exaggerated distortion.
Rooms begin with big planes
Block the floor, walls and ceiling before chairs or windows. Use the same vanishing logic for objects aligned with those planes. An object rotated differently needs its own appropriate edge directions.
Check a drawing before adding detail
Extend receding edges lightly and see where they meet. Watch for a changing horizon, boxes whose edges diverge and shelves that do not share a consistent direction. A ruler can check your construction; the final sketch can stay expressive.
Put it on paper
A small exercise. A useful start.
Draw a horizon and a vanishing point. Add a rectangle below the horizon, connect all four corners to the point, then mark the back face. Erase hidden guides and shade the three planes differently.