To draw from observation, it's important to set up your object and easel properly first. Translating the angles that I'll teach you to measure is much easier to do when standing, though you could use a high stool in front of your easel or sit at a drafting table if necessary.
Ideally, you would arrange your object or still life at eye-level in natural light. If this is not possible, you can use artificial lighting. I recommend an adjustable gooseneck lamp. I can't recommend any particular brands, but you can see a few options in the links provide and then choose one independently. If the light on your object is too harsh, you can use a dimmer bulb or move the lamp back a bit.
options:
Below are a few tips on arranging and lighting your object.
First, it's important to light the object from the side so that you can see the contrast in values that are essential to indicating the form and volume of the object. When lit from the side, the shadow will fall directly to the side of the object (not in front of or behind the object), like this
To find the best natural light in your workspace, watch this
To arrange artificial light, watch this
On arranging your easel and still lifes:
1) Try to arrange the objects or still life at eye level so that you can see the bottom of the object and where it rests on the surface. This will eliminate the challenge of drawing things in the foreshortened view. The dark and light value contrast will also be easier to see.
You could use a shelf, a book case, or put some boxes on top of a desk or rolling cart.
The obvious advantage of the rolling cart is that you can put your supplies beneath your still life, put it near the window when necessary, and push it aside when not in use.
2) Cut and tape two pieces of foam-core together to create a simple white background behind your object and block out the rest of the room. This will simplify the drawing process enormously. Use a third white sheet of paper or foamcore on the surface, as seen below.
In this image, I'm using natural light. You should eliminate any other lights from falling on your object (such as the door, additional windows, or overhead light). If necessary, you could rest another piece of foamcore over the top to block out these lights.
Each light source casts a shadow on the object and you only want one shadow.
In this image, I'm using artificial light.
3) Position your easel on the same side as your drawing hand. I'm right handed, so my easel is on the right. The easel should be positioned vertically, so that you can translate the three dimensional object onto the 2D picture plane. If the easel is leaning back at an angle, the drawing will be distorted.
You want to stand an arm's length from your easel so that you can measure angles and proportions of your object with a sight stick, and then move your arm without bending your elbow to copy these measurements onto the page.
It's best if you can arrange your easel so that you can see both your still life and your drawing by moving your eyes (and not your body)
In this clip, I'll show you how to position yourself so that you can use the sightstick