how did you train your dog?

The ASPCA Complete Dog Training Manual.  Two page layout for one skill.  Good arrangement, easy to read from a table top while you are working with the dog and have the book out for reference.  Information about why behavior occurs,  nice section on management of problem behaviors.

I'm a professional trainer, and all my dogs are trained using positive reinforcement methods, sometimes including clicker training.  I also take them to group classes with my colleagues (until the dogs are adults) so that they will be, and remain, properly socialized to people and other dogs.
Best book you can buy IMO - "The Culture Clash", by Jean Donaldson.  Reading and understanding her book will keep you from anthropomorphizing your dog, and give you a healthy respect for the ever amazing canine species.  I also like "The Power of Positive Training" and, if you have a small dog, "Little Dogs, Training Your Pint-Sized Companion".
I don't believe you should send your dog to a trainer.  I can train your dog, but if you don't learn how to maintain that training, you have just wasted a bundle of money...
If you are really interested in training, and want to learn more, dogwise.com maintains a list of the top ten books for dog owners that is quite good.
If you want to take your dog to classes, these sites have a trainer search:
[linkhttp://www.ccpdt.com]www.ccpdt.com[/link]
[linkhttp://www.clickertraining.com]www.clickertraining.com[/link]

regardless of what trainers you pay or classes you attend, you, the dog owner, will end up doing 99% of the training-- every interaction you have with your dog is shaping that dog's behavior. So I'd suggest getting many good positive training books and go for it. Classes are excellent for older puppies that have some concept of what the basic commands mean.

I think all of the above are great.  I don't think one is a substitute for another... 
 
I think classes are key for socialization and working with distractions, but I don't think trainers in classes are really training the dogs - they are training the people to be able to train their dogs and giving the dogs and people the chance to be around eachother.  I would buy some of the books that have been recommended, start basic obedience at home and then get the dog, while still young or new to the home, enrolled in a group class. 
 
Then, once you have done a bunch of work, if there are any problems or kinks you need some help working out, I would consult a private trainer to come to your house.  I am a firm believer in professional help, if you can afford it, but, based on personal experience, IMHO, it all comes down to the amount of time and effort you, the owner, are going to put in...  I have found that the good trainers have trained me, not my dog [].

 After having gone to some obedience classes a while ago with our previous dog, I decided to train my dog Cassidy, by myself at home. It worked out pretty good and I was happy with how she did. ( She was a very easy and smart dog to train though! []) I took her to an advanced obedience class when she was a little over a year old, to pretty much proof her in her obedience. Then we did 16 weeks of agility at the club. I think that a beginner obedience class really isn't the best place to train a dog, because there are way too many distractions for the dog. I would train the dog at home, and reinforce the behavior in public/at a class if you like. While I still do training at home, I'm going to do another level of the advanced class this summer through 4-H and then take her to the dog show at the fair.

With my puppy Mirelle, I am taking her to a puppy class once a week for the socialization and stuff, which I think is good for her, but I do training at home too.

I trained my guy using the "Playtraining" method combined with positive reinforcement and treats.  Any negative behaviors result in a growl or a snarl from me, but this is aside from the actual training process.  Just don't overdo the length of the training sessions if you have a dog that gets bored easily.

schleide is totally right - all of the above!  It's how you learn what will work best for you and your dog.  It's easy to be steered down one path if you only consult one "source", and being frustrated with results. 
 
Even just OBSERVING a good group or individual lesson can be a good way to gain tips on how to train a dog and manage your own body language/handling skills.  If the trainer is worth their money, they'll explain how and why they handle a dog a certain way and how owners can change their instructions to the dog to make it clearer.  Plus, most good trainers will encourage observers (so long as you don't intrude on the time of their paid customers, obviously).

Yes, Jean Donaldson is one of my favourites, too.
It`s a mix of everything, attending classes with a puppy can be very helpful. But it must be a good class for little pups, you can just observe how they interact, how they communicate by playing and they get socialized. But you have to go on with this process at home and meet other good socialized dogs when you go for a walk so he learns to "behave" among other dogs of every size and breed and not only in class.
It is much better to start right at the beginning and having more work and doing it right (or at least try [], for there will always be a situation when you will think, darn it, I didn`t want to react that way...sigh) than trying to correct a problem later.
When you find a good class at the beginning, I don`t  think a personal trainer is neccessary when there`s no problem.