Getting Started in Homesteading
I'm a firm believer in jumping in and learning as you go. Of course, there's a balancing point. You do need to do some planning and research.
I think one of the easiest ways to get started is in gardening. Even an apartment dweller can usually find room on a small patio or deck to raise some tomatoes and herbs. If you've got more space, all the better--but don't go overboard and plan a huge garden until you are confident you can manage the upkeep.
If you want to raise animals, find out what your local zoning ordinances allow and disallow.
Most urban homesteaders need to generate a cash income in addition to the above ideas.