Take measurements of what you want to draw, (e.g. a simple cube that is 100 cm x 100 cm x 100 cm.) A full scale drawing would require you to draw the cube on a paper 100 cm x 100 cm x 100 cm. If you want to 'scale', you would then redraw using new measurements. So, a 1/10 scale drawing would mean that you would redraw the cube on paper as 10 cm x 10 cm x 10 cm. A 1/20 scale would be 5 cm x 5 cm x 5 cm. The same concept holds for all scale drawings.
