Start with a teacher. A good teacher can communicate skills, clarify background information, answer questions, and help you test your understanding.
Prepare to do some shopping around for someone that “clicks”. There is no one “right” teacher, just a lot of options, some of which will work better for you than others. Most teachers teach or work with groups on some level, so the simplest thing to do is to google around for meditation classes in your area and ask if you can sit in on a class. That way you get to watch the teacher in action with different people. How does he or she treat the students? How do the students treat each other? Is there a hierarchy? Are you comfortable with what you see?
Be clear about what you are looking for, and don’t be afraid to ask how a teacher or group will fit in with your goals. Observe the teacher carefully: look at their website, their literature, their demeanor, listen to the words they use. What is being served? For example, some religiously-oriented teachers may at least in part be serving the perpetuation of their cultural traditions. This doesn’t mean they can’t help you, but in a teacher-student relationship, the progress of the student should take priority. Will it? Watch the interactions, and judge for yourself.
Many people that you meet in a particular class or center — even the teachers! — are committed to a given philosophy or school and know little or nothing about other schools and ways of doing things. Don’t fall into that trap yourself; be broad-minded, sample a lot of things, and understand at least some of the differences before making up your mind. Talk to a number of teachers and/or visit a number of groups. How are they different? How are they alike? Where do you feel comfortable, and why? If you want to grow, you need to challenge yourself, so a certain amount of discomfort is a good sign. But examine it closely. Is it just the discomfort of trying something new, or is your gut trying to tell you something’s out of balance? Follow up your hunches with careful observation, and ask a lot of questions.
Finally, it is reasonable to pay for teaching, generally at about the rate you would pay for a group class in some other discipline or for consultation with a psychotherapist (if one-on-one teaching is what you want). Although some teachers still follow the Buddhist custom of offering teaching on a donation basis, remember that “donation” does not mean “free”. If a given teacher or group IS offering teaching for free, is something else expected in return? What? Why?
Once you find a teacher that seems a good fit, commit yourself to follow his or her instructions carefully for at least a few months. It will take this long to really assess at least some of the possible long-term impacts of the practice. An on-again, off-again meditation practice doesn’t get you very far at all.