One point - sometimes it pays to feed your dog better quality food. One of my dogs was initially eating Purina Dog Chow - since it has lots of filler - she was eating quite a bit of food, and making rather large stools...twice as much to pick up! If you feed your dog a high quality food, your dog will eat and poop less - and digest more of what he/she eats. I can't say I ever did a real exact analysis, but I think it worked out to cost about the same, and her coat improved DRAMTICALLY! Plus, the better you feed your dog, the more likely they are to live longer and better! Another food treat that is inexpensive that most dogs love is eggs.
Read labels before you give your dog 'treats' Many of them are really bad junk - like corn flour as the main ingredient. So you're paying $4 a bag for corn flour with bacon fat and artificial smoke flavor.
A GREAT book on the subject of training is called "How to be your Dog's Best Friend." You can most likely find this at your local library, as it has been around for a while. It is written by monks whose vocation is trainging professional class German Shepherds. I admit that I initially avoided the book, but once I started reading it, it was the best book I ever found. This book has saved countless dogs from being sent to the Humane Society!
Thatpetplace.com has some very good prices. Another option I just heard about is Drsfosterandsmith.com They are about average on many of their products, but you can order meds from them. If you want really inexpensive vaccines though, check out HappyJack.com They are geared towards hunting dogs. I highly recommend a hunting style collar. Nothing fancy, but I really like the ring design on these collars. If you plan on leashing your dog, the ring on these collars is much easier to find/hook up than the typical collar with the half moon style rings (The half-moon rings go flat, and shift around when you try to hook up the leash) Their all-dog collars are durable too.
My last great pet tip is Nature's Miracle and/or Spot Shot for accidents. Nature's Miracle works best in a spray bottle, use it first to treat most spots. If that doesn't work, Spot Shot is strong chemicals, but if you have a stubborn stain; it works. It even works on old stains!