I had mine done by a senior guy at a major east coast teaching hospital. He'd done a couple of thousand of them prior, so I was pretty confident.
He was running behind that day and somehow I never received any pre-procedure sedatives. I didn't know to ask. If that happens to you, ASK!
The first "crochet hook" caught me off guard and I briefly passed out. Seems docs really hate it when you lose consciousness on the table.
I woke up in a second or two and the whole room was flipping out. Something about no blood pressure. Anyway, the second one was much easier since I had a sense of what was coming. When they say, "you'll feel a little pressure," you should get ready.
For a week or so afterwards, you must strap those boys down well. I was feeling pretty good and stopped wearing the jock strap after two days. Big mistake. You don't notice all the bouncing around the fellas do usually, but you sure will after The Big V.