Obviously we all need to learn. There are many ways (see Learning Yoga page). Yoga, hatha yoga in particular, is especially difficult to learn without personal guidance and explanation -- it is one of those fields where book learning as the sole educational tool simply doesn’t exist as an option, although individual learning styles vary immensely, and people will vary widely in how they attain their yoga knowledge & wisdom.
Basically a person is said to have a yoga guru if their predominant knowledge source and inspiration for yoga is a single individual. Usually having a guru includes following the guru’s yogic approach to the exclusion of other approaches (which frequently includes the belief that other approaches are wrong, not simply different). It is generally not possible to have multiple gurus with different approaches any more than it is possible to simultaneously strive to follow multiple sects within religions such as Christianity, Judaism, or Islam. Or sects of philosophies such as Buddhism. If you pick one sect, you follow that one.
Many traditional Masters followed a guru (for example, Krishnamacharya credited his guru Ramamohana Brahmachari), and a belief grew in some quarters that having a guru was an absolute requirement for a serious yoga student. Unfortunately for that belief, very few of the ancient foundational texts, yoga or otherwise, actually say that a guru is mandatory -- gurus are referenced, but in the context of guidance and assistance as needed. The Buddha stated flatly that individual empirical experience was the only valid approach to spiritual growth. The Tao Te Ching counsels personal oneness with the Tao, the Way. In the field of yoga, Yoga Yajnavalkya is quite clear that one should “hold in respect the great sages and teachers,” but that ultimately the “nectar of yoga, which is the cause for destruction of all bondage and leads to freedom” is “born in solitude through secluded practice” by the individual.
You can choose to learn yoga through multiple sources or from one predominant source. Whether to have a guru is your choice; the ultimate responsibility for your yoga practice lies with you. There is a Zen saying, “Seek not the masters; seek what they sought.” Pretty good advice.
No matter how your yoga practice comes into being, it will be endowed with certain traits. To explore the design, development and execution of a yoga practice, please go to the Yoga Practice Design page.