I would go through @Mike_Bee thread The legendary Prince Orobas and Solomon's 72 spirits of the Goetia
There is a post (probably in the first 15 posts) about choosing a patron spirit and working with them to open your clairs. I highly recommend it.
I also recommend reading the entire thread. It is gold.
From personal experience, I can say that once you open the sigil and feel a presence, close your eyes and just go deeper. As deep as you can. Also focus (not too hard) on distant sounds, maybe a clock ticking etc etc. Then whatever your strongest Clair is naturally, communication will come through that. For me it came as a vivid visual and a conversation, the spirit wasn’t speaking, his lips weren’t moving but he was talking in my ear, from the inside. This happened with King Paimon for me (Thank you King you’re a Rockstar and you know it) It takes time and don’t go with any expectations. Just go with the flow. Believing that you’ll accept any form of communication you get, and if you don’t that’s ok too. It WILL happen with time. It just will.
The first time this happens, it’s better than sex followed by a double bacon cheeseburger.
Also physical manifestation, I’ve heard is a much longer process and takes time, I can’t comment on it since I’ve not had that, yet.