I put a lot of mileage in on my bike and I will have to change flats at least once a month and I've had as many as 3 on one ride. The worst one happened when I was in a big pack of riders, I hollered flat but a couple of people didn't hear me and got really mad because they alomst ran into the back of me when I slowed down. Moral of the story, don't assume that people in a group know what you're doing even if you've done your best to inform them.

I found this on youtube...

How to change a flat

I don't agree with using a tire iron for putting the tire back on, I use the heels of my hands. But this is a pretty good video.

And yes.... practice at home a bunch of times. Especially with the back tire.