Welcome to Dreamviews.

OBEs are the same as astral projections, which are induced through sleep paralysis. You can also induce a WILD (wake induced lucid dream) through sleep paralysis, so once you reach that state, with a bit of experience you'll be able to choose whether to astral project or enter a lucid dream. You can only be in one state at a time, either having an OBE or a being in a lucid dream, but if you exit a lucid dream and remain still, you might be able to directly enter into an OBE because your body could enter SP. That's really the extent of my knowledge.

There's a lot of good information in the Beyond Dreaming subforum.