If I'm being honest with myself, I'd have to say I was terrified. I was excited about officially starting my own photography business, but I was also terrified. I thought I had a good idea of what to expect since I'd been working with Amanda for two years, but I knew that doing something even a little bit new has a tendency to throw you for a loop once in awhile. And, of course, this first year in business was no exception for me. It's been unbelievably great, and I've also learned some lessons along the way ... some funny, some embarrassing, some just plain good practices. If you're just starting out in this crazy industry, here's my advice to you*:

Always smile! This is #1 because I think this is most important. Putting a smile on your face makes you more approachable and shows that you really do love what you do.
Switch your camera bag from shoulder to shoulder throughout the day. I wear a Kelly Moore Posey bag allllll wedding day, and I've learned the hard way that if I keep it strapped on one should for the entire day, I may look like the Hunchback of Notre Dame the next.
Be flexible! I'm just going to say it: nothing ever goes exactly as planned. People run late, it rains on an outdoor wedding day, the bride's shoes are missing. Stuff happens and you can't always control it, so I say embrace it. If you're calm, you'll help others stay calm too.
Don't be afraid to ask people to move. What I mean is, ask the bride to move closer to the window when she's getting the dress on. The light will be so much better and you'll thank yourself when you're editing. Same thing goes for family formals. Don't be afraid to ask people to move a little to the left or right to keep everything centered. Everyone trusts your judgement and will more than likely be happy to comply.
Drink tons and tons of water. I have a hard time doing this when I'm not in the middle of a wedding or a session, so remembering to drink water when I'm running around thinking of 101 other things isn't easy. I generally get SO thirsty I can't go another step without water or I come home realizing I drank half a glass of water all day. Yeah, not good. I'm working on it, and I'm learning that staying hydrated makes a big difference the day after the wedding.
Keep the ring bags CLOSED. OK, here's my embarrassing story. At my last wedding, my second shooter and I were taking all of the details outside to photograph them in natural light. Well, unbeknownst (who says that?!) to us, one of the bands had slipped out of the bag we were carrying outside. Yes, THE ring that would be exchanged at the ceremony. Thankfully, 1) the groom found it and 2) he wasn't freaked out about it, but I was still 100% embarrassed that it had happened. What if it hadn't been found?! This is all to say you can never been too careful when handling details or anything else. I can guarantee you THAT will never happen again!
Go above and beyond. You should treat your clients and your clients' family and friends as kings and queens. If they ask for a photo that wasn't on the list, take it for them. If you see someone that needs an extra hand, help them. It's good business practice, but it's also being a good human being.
Gas your car up the night before. I'm one of those people that lets my car go down to the line (maybe even below) before I stop for gas. It's not a good idea, however, to test your car while you're driving around on a wedding day and don't have time to stop. Do yourself a favor and gas up ahead of time. You'll avoid lots of freakout moments this way.
Embrace the embarrassing moments. Guys, being a photographer is not always glamorous. You dance around to get kids to look at the camera, you crack stupid jokes to get people to laugh, you trip while walking backwards (or forwards!). Embrace the embarrassment because the results are worth it.
Treat your clients as friends ... not as a business deal. I have been lucky enough to work with fantastic people. People I want to be friends with. Treating them as such will help you create a bond that will last past the wedding day.