Lightly sketch squares, circles, cones, rectangles and other shapes to give general guidelines to form and construct solid items, which then can be shaped and refined, giving detail and shading.

The classic way to achieve proportion when using a live subject, scenic view or building is to use your thumb held at points along the pencil viewed at arms length

Draw a faint grid on your drawing paper and place a pre-printed clear Acetate grid over your original, the Acetate grid can be constructed with just a ruler creating 1cm squares using a permanent marker pen. The faint grid on your drawing paper can be scaled up depending on the size of your paper, 2.5cm for A4 and 5cm for A3.

Enlarge the photograph up to approximately A4 size, if you require A3 then you have to enlarge to A4 first then use this to go to A3. The many 'Quick Copy' shops can provide this service.
Once you have your photocopy you place a piece of tracing paper over it and trace round it with a HB (Medium) pencil. Then you turn over the tracing paper and go over your line on the other side with a 4B (Soft) pencil. Next it turned over back to the original first side, placed over your drawing paper and using a HB (Medium) pencil rubbed over your very first outline, this transfers the Soft pencil tracing onto your drawing paper.
From this you can commence your drawing knowing that the angles, perspective and ratio will be correct.

Another approach to achieve correct angles in structures is to apply perspective to your artwork, determine the horizon and vanishing points, either 1, 2, 3 or 4-point perspective.