Religion is systematically excluded from discussion in many of the American public schools. This means that the best way to learn about it, especially about religious traditions other than the one one was raised with, involves a process of self-education.
For my own purposes, I have divided this into four branches of study:
1) Particular religious traditions. These include the Abrahamic religions (Christianity, Islam, Judaism); Asiatic religions, Traditional or tribal religions, and Secularism, which includes atheism, agnosticism, secular humanism, and their relatives.
2) Religious organization
3) Religious practice and worship
4) Religious belief
Factual knowledge of nature and its laws tends to support some religious beliefs more than others, but not necessarily a secular point of view. Insight into the human body and psychology can also be applied. Biographies, particularly of religious figures and leaders, can also be infuential. Religious bodies and movements can be examined as social organizations, with demographics, patterns of relationship with nature, and geographic distribution. There are strong connections with areas of culture, including religious literature, and there is some overlap between religion and philosophy. Practices and behavior, and religious artifacts can also be considered. There are connections with families, education, economics, and government. The influence of religion on social structure and change, in different communities, and in different societies is also a useful topic. It is difficult to follow religion from prehistory, given the limitations of the sources, but in antiquity it becomes more possible to follow religion through groups such as the Egyptians and Babylonians. Several of the major religions of the world developed in the classical and medieval period, and can be followed through the modern period to today.
I don't have specific suggestions except to become familiar with your own religious beliefs, or if you claim none, what you do believe.