While many seek to follow a silver cord, or rope to the astral I find this doesn't suit everyone. I find it is easier for some to simply relax themselves into it through meditation and exploration of energy, and allow themselves to drift in exploring a particular energetic flow.
For people I was helping in the past, this has resulted in etheric projection rather than astral, however. Etheric would be more along the lines of the energies of the physical, and your life force, and as such tends to take on a heavier, "lower vibration" more associated with the physical. This can be exhausting and doesn't quite offer the same effect, though it can be useful in studying the life essence of things. If you have difficulty with differentiation, I may suggest seeking "lighter" energy, that leaves you feeling more whispy or floaty, for lack of better terms, rather than the heaviness of ethereal energies.