Having a dog for life is a commitment. Dogs take a lot of time and energy to train properly. If you really want to have the perfect dog, you have to work for it.
When considering to adopt its important to take a good look at your daily schedule. Dogs require a minimum of TWO walks per day, and yes EVERY DAY! It is important that each walk is a minimum of 30 minutes, and should be closer to an hour. Keep in mind that many high-energy dogs will require longer walks.
Besides walking your dog twice a day, you will need time to train him/her in basic obedience and other skills. It's also important to have play time a few times throughout the day.
Realistically, you should consider that you will be doing DOG TIME about 3 hours per day. This of course will vary by your dog's energy level and age. Younger dogs need more exercise because they have lots more energy. Once you get your dog into an exercise routine, less time may be required. Also consider time for love, cuddling, and petting.
If you're really seriously considering adopting a dog, talk to your friends with dogs, walk your neighbor's dog a few times, and visit your local shelters (BEFORE you're ready to adopt).
Really think about if you have the appropriate amount of time before bringing a new member into your family.