It can definitley be beneficial to do at least some research into the different dog breeds before commiting to adopt a dog. Choosing a Saint Bernard puppy might be great initially but coping with a fully grown version may not be quite as convenient.
There are 2 options when considering how to go about teaching an untrained dog a basic level of obedience. There is quite a bit of free and paid information online and offline in books and other courses, or you can hire a professional dog trainer.
Problems such as how to stop your dog bolting out of the door can be overcome with information freely available online and in good bookshops.