One of the most difficult things to achieve when drawing realistically is capturing accurate proportions. Fortunately, there are many tricks that artists can use to draw proportionately accurate figures. The most reliable way to make a proportionately accurate drawing is to use a grid structure that breaks down the drawing into small, easily rendered cells.
Get a copy of a photograph of something you want to draw.
Draw a grid over the photograph. Use a marker. The grid should consist of horizontal and vertical lines, all 1 inch apart. This will cover the photograph with a series of 1-inch blocks.
Label each row of boxes on the side with a letter, starting from the top left of the photograph and moving down the side of the photograph. To the left of the top box on the left-hand side of the photograph, write the letter "A." To the left of the second box down on the left-hand side of the photograph, write the letter "B." Continue down the side of the photograph until you've labeled each row of boxes with a letter.
Label each column of boxes in the grid at the top with a number, starting from the left and moving to the right. Above the first box at the top left of the photograph, write the number 1. Above the box to the right of the box you just labeled, write the number 2. Continue until you've labeled each column of boxes with a number.
Draw a grid over the paper you plan to draw on. If you wish to draw your subject larger than the photograph, the size of the grid must be larger than the grid over the photograph. For example, you may choose to make the lines of the grid 2 inches apart instead of 1 inch apart. This will make your drawing proportionally larger than the photograph.
Label each row and column of the grid you just drew in step 5 so that the rows correspond to a letter and the columns correspond to a number, just like you did in steps 3 and 4. This way, you will be able to pinpoint exact cells in the grid and draw each cell individually.
Draw each cell in the drawing as it corresponds to the matching cell in the photograph. Start with cell A1, the cell in the far left-hand corner of the grid. Every shape that you see in the photograph's cell A1 should match the cell you see in the drawing's A1 cell. Move to cell A2--the cell just to the right of the cell you just drew--and draw the shapes so the cell in the photograph matches the cell in the drawing. Do this for every cell in the grid.
If you're not interested in drawing with a grid, there are other tricks artists use to keep their drawings accurately proportioned. For example, when drawing a face, start by drawing a single part of that face. A good starting point would be one of the eyes. If you start by drawing the left eye of the face, all other parts of the face should be proportioned relative to the size and placement of that left eye. You know the right eye will be the same size as the left eye. In addition, the eyes are usually placed the distance of a single eye-width apart. Pretend there is an invisible replica of the left eye positioned between the two eyes on the face--this should tell you how far away the right eye will be from the left. After drawing the right eye the same size as the left eye, look at your subject and the placement of the mouth relative to the left eye. If you were to draw a line straight up from the left corner of the subject's mouth, where would it hit the eye? In the middle of the eye? On the left hand side of the eye? By asking yourself these questions and then making your drawing to correspond to the proportions of the subject's face, you should be able to draw the face accurately without a grid.