This really should be a two-way street. The very best admins can be seen often. Don't be afraid of the opportunity to have them in your classroom. They should be there to observe not only you but your students and what is going on there. Welcome them warmly and train your kids to do the same. Take some time to communicate what you are doing at that moment. This opens the door for good communication between you and them. Take the time to pop into their office and just say hello and ask how they are doing. Remember that you both have tremendous responsibilities and acknowledging the human side of your administrator is so important. Anytime you have a concern about your job performance or stress on your team level that cannot be resolved on your own first should be addressed with the admin. Be prepared to share what you have done to come to a resolution. Remember that just as much as you would hate hearing someone complain all of the time, approach your admin with that in mind.

Anytime I approach my admins with a problem, I ALWAYS bring a reasonable solution to the problem to show that I want to work with them to solve the problem.
I also try to invite them in my classroom often for special events, to be a guest reader, or just to hang out for awhile and that lets them know that I want them around and value their input, presence, and time.

I 100% agree with everything that as already been posted. I will also take time out just to ask them about their families or what they did on the weekends. It just opens the lines of communication with them. Most principals that I've had are pretty open to discussing their amazing families and they want to feel like a human being first. I also make sure to loop them in on any potential problems I see and if there is a way I would fix it. Always having some sort solution when going to them about problems is essential. It shows that you have thought through what you are asking of them. They may not go along with those solutions but it's great to have some.