It's pretty hard to give solid, objective tips on tablet use because there's a huge amount of variance between what works for people, and a lot of different ways you can use it. You're really going to have to sit down and consciously think about what works for you.
It's probably going to be helpful for you to tape your tablet down somewhere where it can stay, so your experience using it is consistent. The #2 player of osu! does this. Don't be afraid to move it if you find a more comfortable position for it, but be aware that it may ruin your muscle memory temporarily when you do, especially if you're using absolute positioning.
Here are some things for you to figure out when you first start:
- How do you like to hold the pen? The way you hold it to write may not be the most optimal way to hold it in osu!. Azer has a fairly unusual pen grip if you look at his YouTube videos, he holds it at the very bottom of the pen in a pinch grip. Legend has it that one of Cookiezi's secrets was that he held the pen in a way that he also was dragging his pinky on the surface of the tablet, so he had physical feedback on his pen movement.
- Do you like to press on the tablet with the pen, or hover it slightly above the surface?
- Do you prefer absolute positioning (tablet mode, where the tablet area represents the full pointable area of the application, and moving to a point on the tablet area moves to the equivalent point in the application) or mouse mode (relative positioning, where movement is calculated just as if you were using a mouse, in terms of directional movement regardless of where your pen is currently located)?
- What type of tablet area do you like to use? Full tablet area, or a partial area? And if a partial area, how large? Where do you position tablet area at, the center, the corners, or somewhere else? Some people like to use tape to mark off their tablet areas, so they have a visual and physical reminder / restriction of the bounds of their tablet areas. Remember, the balance between large and small tablet area affects the balance between your precision and your speed, where a large area will help your precision and stability but hinder your speed, and a small area will help your speed but hinder your precision and stability.