hello

I learned 3D by myself, and I have, so far, created some objets using Moi3D (the best software on earth).
Now, I would like create a complete room, and I've got a question.

How people know some basics informations as a door heigt, laptop thickness...

I've seen blueprints on many websites for specific objet (plan, boat...) but not so much for common objets.
Do people take 3 photos (top/face/side) of objets, should I train to be able to create a 3D model from a single perspective picture (found on "google image") ?

As far as blueprints are concerned, When you create 2 objets from two blueprints, how do you adjust there size, because a chair is not the same size as a plane.

Thanks for any advises.