I had my first tri experience today as well and it also went quite well. I did the Danskin triathlon in MA, this was quite a large race (2100+ women) but comprised of about 80% newbies. It was a sprint, 0.75K swim, 20K bike, 5K run. I was extremely happy with my solid middle finish (in top 50% both age group and overall).
Well I have to say, for a first time women triathlon the Danskin is definitely a great way to go. Lots of support between competitors, amazing volunteers, etc.
My lessons learned include:
1) Make sure you use a bike you have LOTS of practice with. Over the past couple weeks I thought I had gotten used to a new bike. Well, turns out is really easy to shift into the wrong gear up a big hill on a bike you aren't used to- Multiple times - completely blowing your whole bike time. I did end up going with the right bike but I needed more practice time with it.
2) Know your strengths and use them despite standard newbie advice. I am a swimmer and thank goodness I had time to practice open water. Only because I am a very strong swimmer I was very glad I positioned myself in the front middle of my wave. I broke away from people quickly and had nice smooth water.
3) I was in for quite a shock when I started running into people from the wave before mine (and the wave before that) because now I had moving targets to avoid. This was unusual to me since I didn't have practice swimming in packs of people. This is something I will get more practice with. It definitely slowed me down, but I still finished top 4% overall and in my age group for the swim.
4) Don't stand up before you have to! I didn't swim long enough. Nor did I remember what I had been practicing which was to get those feet kicking near the end to make standing and running easier. While out of my wave I was in second in the water, I ended up 5th by the time I reached the timing mat with a likely siginificant time difference since a mere .1 seconds seperated me and the 20th better person.

Overall it was a great race. I'm definitely hooked. And I now have many things I can work on improving!

i had my first tri last month and this is the lesson i learned, triathlons are not as complex as you think they are going to be, its actually pretty easy,

lesson learned from second tri, get a triathlon bike, if you want to participate in the awards ceremony, a tri bike is beyond essential

I tought myself how to swim 5 months ago and got on a bike for the first time in 18 years 5 months ago, today in an Olympic distance I finshed first in my age group of 30-34, 15/160 overall, in my first tri last month which was a quarter ironman, i was 48/205 overall, one month, only difference i went from a road bike to a triathlon bike

stewarba, congrats on your first Tri! Definitely the more open water swimming you do and more tris you do, it gets a bit easier to deal with the washing machine. Though for me the panicky sensation has never completely gone away.

m2tall2 - congrats as well! The Danskin races are so much fun, but yeah the swim can be a pain for faster swimmers. Lots and lots of waves in front of you to swim through...

Spazz - congrats on your first couple of tris. Not sure I agree about the tri bike though - I did all my first tris on a road bike and waited awhile to know exactly what kind of bike I wanted to buy before investing in a tri-specific bike. Podium placing has a lot of different components to it: the course, the conditions, the other athletes who are there. You can place in one race and not in another and it doesn't necessarily mean that you were faster/better in the race you placed in. I have placed everywhere from 1st to 1,000th in races over the years, and it reflects a lot of different variables, but doesn't necessarily correlate to speed. Important thing in my book is to do your best and have fun. New triathletes can go a long way with a good road bike, and depending on the course it is sometimes preferable to ride one (says me, who just did an Olympic bike course with over 40 sharp turns - I was hardly on my aerobars the whole race!!)