Once you've decided to take your photography to a whole new higher level, there is a huge support network on the net to support you which is great because even with the increasing sophistication of digital cameras, there is a lot to learn.
What's your end game?
The consensus on the best place to start seems to be ironically at your end game. How good do you want to be? Do you want to become a more skilled amateur and improve purely for your own pleasure or at some point in the future, would you like to move into it as a profession? Do you want to excel in portraits, landscapes, events? What kind of photos do you most love taking and looking at?
Kicking off with the end in mind simplifies how to start and deciding on what kind of camera to buy, books and courses to invest in, clubs or professional bodies, forums and discussion groups to join.
What level are you at now?
To measure improvement, there's a school of thought that says you need to have a realistic view of how competent you are now. Have a look at the online guide George Burr has posted to help photographers assess this. Ralph Nordstrom also has some interesting things to say on this subject that are worth thinking about.
Research the best learning options for you
Classroom, clubs, groups, books, forums – what is going to work best for you? Don't be in a rush to decide as spending a little time on researching these can save you a whole lot of money.
Enjoy your craft
Be careful not to get so bogged down in the theory, you spend more time on learning it than practising your craft. Shoot more. Try the tips and techniques you are learning about.
Good links to explore:
Peter - 10 years ago
I learnt a lot about taking good photos by going to watch photos being judged by photographic society critiquers.