Anything. Just burn some virtual gas! If you have a 3D plane, find a plane that flies like it....and modify it to fly even MORE like it. That way you can really practice. However, I find that the easier planes to hover (like the big 50% Edge and the 30% Dalton Extra are my 2 fav's to fly because I can hover them all day. It allows me to practice different attitudes of maintaining a plane. Later, I can move to a harder plane to hover. It's like a stepping stone for me.