For me I look at th object really close, like a window or wall, then put my hand slowly through it, then moving the rest of me through - seems to work for me. Running into it you are ALWAYS going to have the thought of hitting it in the back of your mind.

As for flying, climb a tree or a building and jump off. I have trouble getting off the ground, so go up to a high place and jump, then swoop down and fly up, works every time