I keep it simple. Her orgasm is her responsibility. Some like to be on top, others like me on top, and others require oral, and still others any combination depending on their mood. I figure my job is just to stay hard and let her move into the right angle and she'll get there. If not, oral is almost 100% positive. My wife will tell me on any given night she just can't get there. At those times, we have a couple vibrators which can actually be pretty hot also. It doesn't get much hotter than her cumming while you're filling her mouth with baby batter.
The only thing that's strange to me is that as hot as it is to watch a girl get herself off, it's usually totally different than what I can do. In other words, it's impossible to duplicate her method. And where it may take me 15-20 minutes to get her there, she can get herself there in 5 minutes or even less.