There's a crucial advantage that long-time athletes have over those of us who came into triathlon without much of an active history (or, in my case, a history of something with almost no direct skill correlation, i.e. American football).
I've seen the difference in athletes I coach who started swimming at an early age. True, they haven't swam seriously in twenty years, and were never much good in high school or middle school or whatever age they left that sport. But they've retained so much technique from that time swimming as kids that they leave my other athletes in the dust!
It's sometimes frustrating to look at these athletes and see them swim by me like I'm standing still. I'm in the pool with them. I'm putting the same amount of training time in (well, not currently, but I was earlier in the year). I swim my heart out in races. And they're still able to finish minutes ahead of me.
What's even more frustrating is knowing that it took them at least a dozen years to build up the muscle memory and kinesthetic awareness to do something that is very difficult for humans. And so if I want to swim with anywhere near that skill level, I'm looking at spending the next 10 years or so refining technique and training by body and mind to work properly in the water to propel me forward.
On the other hand, knowing that I have such a long way to go means that every time I get in the pool, I have a chance to get better. Not faster, necessarily; at least not right away. But better. Each time you swim, you can refine the entry a little more, work on keeping the elbow higher, focus on your body roll. Because you, assuming you haven't been swimming since you were 4 years old, can always improve, you can always be earning a little more speed, a little more efficiency from your swim stroke, but without the pain and suffering of trying to hit interval after interval at a specific speed (which is what your teammates who've been swimming since they were 4 years old will be doing to improve their speed and efficiency).
So here's what you do.
Have yourself evaluated--swimming, biking, and running. Doesn't have to be by a coach. See if you have at least one friend who knows enough about sport that they'll know what to look for when they watch you swim (or bike or run, but we all know that technique means most in swimming, right?). My college roommate was one of those 4-year-old swimmers (her mom was a swim instructor), and she used to watch me and give me tips. I have one athlete who's benefited greatly from the collective "expertise" of our gym's lifeguarding staff.
That said, you will greatly benefit from working with a coach. If you're in Kansas, I can help you. If not, check with your local tri team (and you should be a member, if you're not already) or a regional YMCA or another local gym. Just make sure that the gym actually has a pool. If you're looking for someone to help you with your swim, make sure they know what they're talking about. The head lifeguard who teaches kids' swim lessons is not going to help you. The masters swim coach will (probably). Your best option is to get with a swim or tri coach who has swimming experience and coaching experience specific to triathlon. And if you're going to spend the money on having someone help you, why not get the best value you possibly can?
Technique is most crucial on the swim, but it's also important when cycling and running. It shouldn't be hard to find someone to help you with run form. Again, a friend who's been running for a while will do. I've had local track and cross country coaches who have been willing to offer advice to me and my athletes. Or you can check your local running shop for a coach in your area. My local running shop has a team that has a weekly track workout; if you have something like that available to you, you might get some help with coaching there. For cycling help, it's a little tougher. If you can find a spinning workout coached by an actual cyclist (as opposed to a group fitness instructor), that's probably ideal. See if you can bring your bike in on a trainer, and let the instructor know that you need some help. Might want to feel out the different classes; not every spinning instructor is going to be willing or able to help you, so try a few classes before you approach someone for help.
Besides getting some objective help on your swim, bike, and run, you can read up on what constitutes good form. Read books. Read articles online about what good form looks like. Try to get an objective sense of whether or not you're doing those things. Try to feel your body doing those things.
And once you've got an idea--both objectively and subjectively--of what you need to work on, it's time to drill. Remember, at this point, technique will still do more for you than speedwork. So why would you spend more time sprinting than you do on drilling? Doesn't make any sense.
You guys got the take-aways, yes? Get someone to watch you and analyze (nitpick) your form. Learn as much as you can about good swim, bike, and run form. And then make drills your priority, especially in the early and off season. And keep in mind that although the ex-collegiate-swimmers and cross country runners might have you beat in the technique department, that means that you'll always have something to gain from technique and drill work.