Learning kung fu without an instructor is much more difficult than learning it in the context of a regular class taught by a qualified, experienced sifu. However, not everybody has the schedule, disposable income and proximity to a dojo that's necessary to go to a kung fu class. If you're in such a situation, you can develop basic kung fu skills on your own with resources available in a variety of places.
Set up your training area. You will need a space with at least 15 feet per side, preferably with a soft floor, such as a carpet or thin mat. Hang your punching bag in one corner. If your ceiling won't accommodate a hanging bag, you can find a free-standing bag at most sporting goods stores.
Decide what style of kung fu you want to study. There are dozens of kung fu styles available, each with its own quirks and unique aspects. You can view examples on YouTube and other user video sites until you see one that catches your eye. Wing tsun, wushu and kenpo are common styles.
Find instructional video. You can order these from "Black Belt" magazine or Century Martial Arts, find them on user video sites or in public libraries, or check kung fu school websites for tip videos. Focus first on yellow-sash techniques, such as horse stance, reverse punch, front and round kicks and crane stance. As you master these techniques, you can move on to more advanced skills.
Select one or two skills to practice at a time. Watch the skill on video until you feel you can practice it, then move to your training area. Focus intently on your stance, regardless of what kind of technique you are practicing. Kung fu stances provide the power to all strikes and are intentionally low to help you build leg and core strength.
Seek constant feedback by talking to kung fu practitioners. One way to get feedback is to post video of yourself on a martial arts forum such as Martial Talk. Although you'll get a fair share of negative comments, a handful of users will give you sincere and valuable advice.