Research urban dance genres. Urban and street dance encompass a wide variety of styles. Try one out that best speaks to you, best fits your style or even takes you out of your comfort zone. A handful of beginner classes are titled "urban dance" and focus on choreography generally inspired by hip-hop. Dance styles include popping, breaking, hip-hop routines or locking, among others.
Write down your top style choices. Watch online videos of performances in those styles to further narrow down your choices. These also give you a jump-start on learning moves.
Find a beginner's course in your chosen style. Styles and classes vary widely, depending on troupes, schools and studios in your area. Research class content, pricing and schedules on the school's website, or contact someone at the school. Research instructors' backgrounds and read up on their teaching styles, if available. Ask about a free trial class before you enroll. Repeat this for several schools, if available.
Attend your trial classes. Observe how the instructor interacts with the students and how students behave toward her and one another. If you're enjoying the class and feel challenged, but not overwhelmed, that's a good sign. Repeat this in each trial class, then make a decision and enroll in a course you enjoy.
Attend every class. Arrive on time and in appropriate attire per you instructor's guidelines. Arrive early to warm up to protect yourself and shift gears from the day's prior activities. Be courteous to other students, and concentrate as much as possible during class.
Practice every day outside class. You learn dance by doing it, allowing your brain and body to memorize and perfect movement and technique. Watch online videos, and attend performances as often as possible for inspiration and exposure. Search for and enroll in workshops in your area, or look for camps and longer-term programs if you're able to travel at any time for instruction.