1. Improvisation is a big no-no
You should draw what you see, NOT what you WANT to see.
2. Pencil
Make sure you use a good quality pencil for your diagrams.
3. Simplicity is what’s preferable
Try to make your diagrams as simple as possible.
4. Drawings should be done on an unlined sheet
Biological drawings must be done on unlined sheets for more authenticity.
5. Biological drawings should be conspicuous for easier comprehensibility
Avoid crowding parts of the diagram.
A biological drawing have all relevant parts that are conspicuous enough to the human eye. It should also be large enough to present all intricate details of the diagram to the observer.
6. Labeling and positioning
It is more advisable to keep your diagram to the left-hand side of your page. You should use the right-hand side for labeling purposes.
A few more worthy mentions…
 All biological drawings should be titled.
 Shading specific areas of a diagram might look aesthetic to the eye, but this practice is not acceptable in biology. Hence, the advice is to AVOID at all cost.
 Try to draw the diagram on a single stroke of the pencil. Multiple strokes need to be avoided at all possible costs.
 Labeling intersection of lines aren’t tolerated in biological diagrams. AVOID.