Choose how far away you want to be from the object you're sketching. For starters, don't pick too far away or so close you're practically on top of it. A comfortable distance may be about two or three feet away. Maybe even four feet away. What is comfortable for you may not be comfortable for someone else, so experiment. Being able to see accurately, and if you are nearsighted or farsighted perhaps, may come into play.
Also, remember for the future that a close-up view not only looks different than a more distant view but also has a different quality. The closer view is more intimate, but that may not be the perspective or mood you want. Vermeer used both distances to great advantage, especially close intimate portraits of people engaged in sewing or other activities, whose eyes held mystical glints as if surprised. A moment captured! The farther away one is from the central object of attention in a painting or drawing the more epic or "universal" (rather than intimate and personal) the feeling. The Last Supper would have been very different had Leonardo chosen to get closer to the table.
Remember, we are talking about learning how to draw a straightforward object, that simple glass, so get as close as you need to it to really see it well but not too close that the image blurs or you lack physical motion of your arm and hand. The angle you decide to put your paper at will determine whether you are drawing the glass straight ahead, from the top, or perhaps looking upward at the rim. I prefer for the purposes of this initial exercise that you draw the glass with a small oval at the top rim, slightly from above, but not so much as to have the top of the glass be a true circle. Why do that? You wouldn’t see the sides of the glass that way.
Find yourself a comfortable chair so that you are not compelled to squirm and lose your angle of view.
Position your drawing paper or pad in front of the object but sufficiently below the top of the object, so that the pad or paper is not blocking your view of the object and you won't have to peer over the sides or top of the pad, paper or drawing board. You can lean the pad slightly on the edge of the table or if you have a tilting table that will hold steady, use that.
