Here are the basics to learning perspective and construction drawing, from simply drawing line to one and two point perspective. With these 8 steps you can learn the core skills to apply to construction drawing, design, and other types of formal drawing.

Step 1: Line Exercises

Starting by learning basic straight line technique will help you with the more complex skills.

Steps:

Make 2 points and draw a straight line in between the two
1. Lock wrist and use arm to achieve straight line motion
2. Not too slow (line may be rough), but also not rushed (the line might be inaccurate, go past the second dot)
Draw over this same line 8 times
Repeat

Once you have repeated the lines enough that you feel that you have mastered them, making sure they are straight and consistent, you can move on to curves.

Step 2: Curves

Curves are similar to lines but utilize the curve of your wrist that you want to try and avoid when drawing lines.

Steps:

Lock your arm in place and use the natural curve of the wrist to draw a curved line between two points.
Draw over the same line 8 times
Repeat

Repeat enough times that the curves are consistent. Try curves of different sizes. Still utilizing your curve, you can move on to ellipses.

Step 3: Ellipses

Ellipses are even circles or ovals. There are two methods of drawing ellipses, the latter will get you more exact shapes.

For small ellipses, ghost by moving arm (for large ellipses)/wrist (for small ellipses) while in motion, lower the pencil down on to the paper. This will get you used to the motion of the ellipse before you put your pencil to the paper, and it will make it more precise.
Repeat

Draw box using straight lines.
Draw ellipses inside of the box, starting a new ellipse at the midpoint of each previous circle, to make even shapes.
Repeat

Those are the basics to learning 2D renderings. Now you can use these skills to create 3D shapes and perspective.

Step 4: Learning Isometric Shapes

There are two basic types of 3D angles/shapes, Isometric and Oblique.

Isometric shapes are made up of straight lines facing the same direction do not converge to a single point, but remain parallel no matter what direction they are facing. Isometric shapes refer to a non-frontal facing view on an object, or at a corner.

Step 5: Learning Oblique Shapes

An oblique drawing starts with a straight on view of one of the object's faces, which is often the front face. Angled, parallel lines are drawn to represent the object’s depth. Straight lines facing the same direction do not converge to a single point, but remain parallel no matter what direction they are facing.

Step 6: 1 Point Perspective

Perspective!!! Perspective drawing will really allow you to accurately represent 3D objects on a 2D picture plane, and is a perfect culminations of the skills you have learned so far. There are 3 types of perspective drawing, 1 point, 2 point, and 3 point (which we will not cover, as it is less relevant, far more difficult, and comes up less often). You can implement perspective in anything from architectural work to object design.

1 point perspective is similar to oblique where one plane remains flat and facing the viewer, side planes and vertical planes converge to a single point on the horizon line. All vertical lines are parallel.

Steps:

Start by drawing a horizontal horizon line and one “vanishing point” somewhere on the line.
1. The vanishing point is the point on the horizon line at which all of our lines will go to.
Draw the vertical lines, they have nothing to do with the vanishing point and will be completely vertical.
Then draw the horizontal lines completely horizontal with planes/sides of a shape that run parallel with the horizon line.
The remaining sides will run towards the vanishing point.
1. This means that if you extended your line it should run straight through the vanishing point.
2. Do this on all lines in planes that do not run parallel to the horizon line, and are not vertical.
Darken the outlines of the shape to distinguish from the lines going to the vanishing point and the space around it.

Once you are able to master this with a variety of different shapes (moving on from simple cubes), try 2 point perspective.

Step 7: 2 Point Perspective

2 point perspective is similar to one point perspective, but instead there are 2 points of conversion on the horizon line. Typically, 2 point perspective is used to describe an object where the corner is visible, that clearly heads towards two separate vanishing points. Just like in 1 point perspective, all verticals will still remain parallel.

Steps:

Start by drawing the horizon line.
Draw the corner of the box using a vertical line that is closest to the viewer.
Draw light lines that converge to each of the vanishing points on the horizon line.
Next, draw the receding corners of the box using shorter, vertical lines.
Lastly, darken the outline of the box created to separate the object from the space around it.

Okay! Hopefully you've mastered these skills and can move forward to shading, to bring realism to your drawings and make them more impressive and interesting.

Step 8: Basic Shading

After learning all of these techniques, you can incorporate shading into your drawings to heighten them even further. Shading is a pretty easy concept to understand. Shading comes in when determining where light and shadow are in your drawing.

Planes directly facing the light source will receive the most amount of light, therefore being the brightest areas on an object.
Mid-tones indirectly face the light, and will appear less bright than planes directly facing or directly opposing the light.
Dark Tones receive little to no light, and are always darker than planes facing the light source.
Cast shadows help to “ground” an object and to establish a sense of space.

Here, we are using a hatching and crosshatching technique, which is made up of individual lines that get closer and darker in the darker areas and lighter and more spread out in the lighter areas. You may also simply shade completely, just varying the tone or weight of your utensil.

Hopefully this tutorial has been helpful! You can implement these skills with a variety of different drawing styles and subjects, and use these basics to further explore drafting.