My wife usually ejaculates when we are having sex. It's normally not her first orgasm, but second or third. Mostly with a vibrator on her clit. She claims that she can tell when she's going to squirt and be able to go for it or hold it in...but it gets harder to control it the more orgasms she has.

It's pretty exciting for me to watch, but make sure you have towels down or there will be a huge wet spot somebody has to sleep in!

I really enjoy rubbing her g-spot when she's close...it's almost like I can control how fast the squirts come by how fast I move my finger. She also occasionally will squirt when I'm licking her clit which is also a huge turn on.