(picture found at http://legardenie87.blogspot.jp/2010/03/i-dont-know.html)
In English, it translates as "Thank you in advance." This is true, but it's a literal translation one thinks about; and so it's not quite understood with words alone. If you don't understand completely, it's not because you're stupid because you're supposed to understand, it's just you probably haven't had much experience with the term. We also certainly don't need to repent. Just go into the world and say onegaishimasu. After being in situations where you onegaishimasu, you begin to unfold understanding. Onegaishimasu is a kind of "please." You say this word before you start something with another force in which you will commit yourself to understanding. When you say this word, you humble yourself, and make yourself an "empty cup" as the saying goes.
After you say onegaishimasu, you begin a process of uke. As an uke you receive something. One could say we are an uke when we watch or listen to media, ride in trains and cars, or consume things like food, drinks, drugs, etc. For modern people living in first world nations, we spend a lot of our time in uke, but I don't think many people notice this phenomenon. That's OK. Again, if one doesn't understand, it's not because they are stupid, they just haven't had experience saying the word, or abstracting about the concept. That being said, it's not like we as moderns are redefining uke with all the stuff we are receiving. This is an ancient term that applies to all humanity from it's beginning, which is nature; past, present, and future. When we uke, we are essentially receiving, but we are not completely passive. Our participation depends on what and how we receive it, but no matter what, we are participating. We are uke when we are sitting on the couch watching TV drinking beer. We are also uke when we are fully engaged in an aikido technique being thrown or put into lock. We are uke when we taking notes in a classroom. We are also uke when we bow before entering a shrine. It's a term that applies to a wide variety of situations, and yet it's a very specific part of the universe.
I don't know, so I go to a teacher and I say, "onegaishimasu." Then I begin uke. This is very easy for me because I don't know much. It's very easy for me because I've had a lot of good teachers. A good teacher is a balance of intelligence (practical ability) and benevolence (honesty).
I went to an aikido seminar today, and I'm absolutely overflowing with things I want to say, but it's too much right now. This is what has been written. As time passes, I will grow farther away from the experience and may not discuss all of the different aspects of the experience. But that's alright, because it's all the same.
Anyway, this is all for now.
Be conscious of your uke! Are you thankful? Dissatisfied?
I don't know!
(Picture found at http://landsofwisdom.com/?p=3073)