There are a lot of ways but there are main principles regarding this.
1st. is cleaning. You can choose any mantra for that you want, such as SURYA.
2nd is empowering. You can use Runes here as well. Mantra for 3rd eye is THAUM. For Pineal Gland is GAUM. Also doing SAMMAS meditation which you can find using search function helps it as well.
3rd is using the "muscles". Say it's like practicing a skill. You empower and clean your Chakra related to the skill you want to learn, so in this case it's astral sight / hearing and so on. Sight is usually the first astral sense you want to open. So you have to do constant visualization exercises in order to get accustomed to using the muscle, or in this case it's the Chakra. You can find Sigils or signs of power to look at in 6 months programme and print them out or draw them by hand. Then you have to look at them intently and after a while close your eyes and see the image and hold it for a while. After you can hold it for a few minutes you have to go to the next stage which is visualizing the image with eyes open. All of this is written in 6 month program, if you can't find it anywhere on the forums let me know, I'll upload it.
Also, do FINAL RTR daily, as it connects both cleaning and empowering aspect, plus it is removing binding and curses from your soul. So it's kind of a killing a lot of birds with one stone deal.
After you open your sight which may take even up to a year, depends how much dedication you will put into, then you move up to sight and so on. After that comes synthesis, meaning combining two or more astral senses at the same time. Main thing is to work on this daily and have a routine you enjoy.