There may be those that ask what making friends with your higher self has to do with relationships. I would argue that it is your primary relationship and if your relationship with your higher self isn't right, the rest of your relationships can't be right. When you have a close relationship with your higher self that is loving and kind, all of your other relationships are able to be loving and kind.
Wikipedia defines the higher self as: an eternal, omnipotent, conscious, and intelligent being, who is one's real self. What the higher self is is beyond evaluation, but I can say that it is your direct connection to the divine and the truth of who you are. It/he/she knows all and loves you unconditionally.
You are connected with your higher self in every moment, you always have been and always will be. That connection can't be lost, so you aren't looking to connect with your higher self. The goal is to become aware of that connection and to develop a close relationship with the higher self. Having an intimate friendship with your higher self is to have an intimate friendship with an all knowing being that loves you deeply no matter what and whose purpose is to help you in any way that it can.
There are many ways of developing a friendship with your higher self, none of which are right or wrong. However, there may be some "techniques" that work really well for you.
Here are some great sites to help you find techniques to do just this:
The above articles have great ideas.They are all useful and if you feel moved to do so, try all of them and figure out which ones help you to feel really connected. However, the most important thing is to invite your higher self to be with you always and ideally to develop a constant dialog with her/him until he/she becomes so much a part of you that you actually are your higher self.
Please do further research on what your higher self is and what you can do to connect with it/him/her if you feel inspired to do so. It's a very worthy cause, there is not a more important relationship that you will have.
Something that you can do today is start a conversation with your Higher Self. I talk to my Higher Self when I'm driving, just to chat, sometimes to ask for her help with something. I talk to her (silently) when I'm grocery shopping so she can help me pick out the healthiest food that my body needs the most, or sometimes that someone in my family needs the most. I talk to her when I experience a challenge in one of my relationships and ask for her to guide me to love and closeness with that person. I talk to her all the time, it's an ongoing conversation. She has become the voice in my head, rudely interrupted on occasion by my ego. You'll know the difference between your higher self and the voice of your ego because your higher self is loving and wants connection with others and your ego is fearful and wants to separate you from others. The ego wants you to be more important than others and lives in lack. The higher self knows all and wants you to contribute and share and lives with faith in absolute abundance.
Ask for her/him/it to come into your life, and she will. Like any relationship allow it time to grow and develop. The rewards are incredible.