- i am far from a professional, but here are some tips that i've picked up!
in case you can't read my handwriting + some deeper explanations:
> never work on a pure white canvas!! it can be really bad for your eyes in the long term, + if you're going to have a background in your final piece, it's better to have an idea as to how the colors you're using will look on the bg
> use references as much as possible!! this is really big! even if you've drawn something a million times, it's always good to check. i'm guilty of not using references sometimes, but it's super important to your growth as an artist.
> don't delete your sketches/layers!! this is kind of a psychological thing and a practical thing rolled into one. by deleting your work you can demotivate yourself, plus you'll lose work you might want to hang on to.
> try not to use pure white!! the example i gave was the eyes. in the first one, the sclera is pure white, and in the second one it's a very very light yellow- a tiny difference, but it's there! white reflects the colors around it so the "white" of your eyes or your teeth would reflect your skin tone.
> shading oh boy. i gave the example of (poorly drawn) spheres. in the first one, i shaded with reddish brown and a light yellow. in the second, i shaded with black and white. in the third, i shaded with reddish brown and a light blue. the first and the third spheres have a lot more depth than the second one, which looks flat and murky in comparison. black and white tends to do this to your colors. the difference between the first and the third one is the warmth of the light source- in the first, it is warm, whereas in the third it is cool, putting them in completely different environments. don't be afraid to play with colors!!
> the dreaded corner i don't know if you can tell but i drew a little color picker there. try to avoid that upper right corner!! it is too saturated and leaves you nowhere to go if you want to shade with a brighter version of your base color, not to mention the eyeburning. there are so many more colors you can use, you don't need to use the brightest possible version!!
that's all i could think of off the top of my head, i hope these help ^^



