As the title said, what was the first thing you learned when drawing, sculpting, 3d modeling, animating, photography, conceptual art, etc.? It could be from school, yourself, or even from peers.
Also, did you find these techniques essential or a good start? If not, what do you wish that somebody told you before starting that art form or wish that you learned before learning the other aspects of the art form?
For me, what I learned first was studying shadows and differentiate values. I found this really helpful as it emphasizes form. I'm not entirely good at it yet, but I found it beneficial when creating three dimensional objects.
I've always loved to draw since I was a kid, but when I was about 12 or 13 years old, I discovered a digital pet website (Neopets) and their drawing community. My dad owned a drawing tablet (I think it was the very first Wacom Graphire?) for his photography hobby, but ended up never really using it. So I asked if I could borrow it.
From that day on, I practiced endlessly on how to use the tablet and various drawing programs. Oekakis were extremely popular and I used them almost exclusively for years.
I'm now at a place where a tablet feels like a natural extension of my own arm, and I'm pretty familiar with how digital drawing programs function. :) I learned that the ability to draw is not just being able to draw things, but also understanding your mediums. I can do some pretty nifty stuff with Paint Tool SAI and Photoshop, but I barely know how to use colored pencils as I never practiced much with traditional mediums the same way I did digital.
So, knowing how to use your mediums is just as important as being able to nail anatomy.
I think the most important thing to learn about a tablet is that it takes time to relearn your hand-eye coordination. It will feel awkward and most people struggle at the beginning. Using your tablet as a mouse to do random browsing with is a great way to get a good feeling for the tablet, without frustrating you because drawing is hard. I think on average it takes most people 1-2 months to get a good feeling for it and be able to draw without thinking too much about it!
So, allow yourself time to adjust. 99% of people who are awesome with tablets had to go through this. Don't give up!