After becoming comfortable with meditation, I would then recommend learning how to direct your focused attention for specific purposes, such as using Qi Cultivation techniques.
But if you are to learn to travel to the astral plane, you first need to train your mind to remember your dreams, and then interpret your dreams. This is pretty important. Why? Because often the information and experiences from the astral plane will at first only be remembered via your dreams. Eventually, you will be able to recall the astral visits and information obtained on the astral plane outside your dreams, but initially, most information will come to you via your dreams.
Dreams are a good way to receive subtle messages, so being able to tune in, receive the message, and then interpret the message is a foundation from which much more complex messaging will be built upon.