Sketch what you like. I mean that literally. If you are trying out your tablet via tutorials you may make a good attempt, but if you draw what you like it will drive you to draw it like you want to see it. What the first time is not so good! You'll draw it better the next time. Mind you, I'm not the step by step guy here. I do doodle and to digital doodle is the same. I want you to feel your pen and the tablet.
When I first used a ball point pen for doodling it was messy. Eventually the character of the pen lines plus the occasional ink globs were no longer an unexpected event. When you know what to expect, you trust your tools. Now you can let ideas come through your tools. It is the same with using a paint brush as with a digital pen. You are learning the parameters of the media, the feel, the control, what the output is. Sketch what you like and think about the process. Adjust your input, grade your output.
What I like about drawing and painting digitally, no waste of paper or canvas when trying out stuff or doodling. I can print if and when I want on what ever media the printer will accept and also print via 3rd party printers.
Again draw what you like, that is a motivator. I've been into designing homes using quonset huts and steel cargo containers. Here is a sketch on the digital tablet I popped just before writing this blog post.
Now I can pick up a tutorial or two on fine points like perspective, shadows, texture, color, line types. And make use of computer stuff that makes digital drawing so great like undo/redo, erase, layers and masking.
Now some words from the master Yoda concerning knowledge of the (creative) force. Doodle or doodle not, there is no try, just doodle!