I always draw a rough sketch on paper to get the composition right. It is so much easier to rub out on paper!
Once you are happy with your drawing, there are a number of ways in which you can transfer that drawing onto your canvas.
1. Just say you used an A4 scrap of paper to do your initial drawing. If the canvas is 2 times larger than the A4 paper, then all measurements are multiplied by 2. You can change the size of the paper so that when multiplied 3 or 4 times it is easier to work out. I use this method most of the time.
2. Some people who find drawing a little difficult use Transfer Paper. You place your blank canvas down first, followed by your transfer paper (graphite side down) with your image (your drawing, or photo or photocopy) on top. Use a sharp pencil or pen and outline your image, including any details (no shading). You can then fix up the drawing freehand.
Barbs Composition Techniques
The focal point of your picture as a whole, should be central on the canvas – i.e. the outermost left point should be equal to the outermost right point of the subject. Similarly the top and bottom should be of roughly equal distance from the edge. This enables the viewer to be drawn into the subject from all angles.
Of course this isn't always the case - when all is said and done, whatever looks good has to be right.
Below is an example of how I rearranged this composition from the original photo.
Don't chop random objects off the canvas unless it is intended as part of a theme.
With landscapes, the "thirds" rule is the most common. The horizon is one- third of the way down the canvas, or two-thirds. Below is an example of this. Note how the river leads the eye into the painting towards the horizon. This also helps to give the painting depth. I always draw a level horizon, even if it is eventually covered with trees etc. I use a ruler to ensure that it is level, then I know that everything drawn around or on top of this line is level as well.
Portraiture is very different to draw in that the likeness and proportions need to be precise. I draw up one horizontal line and one vertical line indicating the box in which I will draw the portrait. I then will measure from these 2 lines only to draw in the portrait's details.