A post I read on another website made me think about this. Someone had asked a group how they invoke/call upon Hekate/Hecate in their rituals and the like, and since I work with Her, it caught my eye. I was reading through and it was the same stuff I usually see about invoking and the like from books. Nothing exact, that I could tell, but the same setup: set up your altar, call quarter, say this long invoking chant, etc. I don't do that. I never really have. I mean, I tried it for a while when I was fist beginning, but I found it way too formal and distracting, more than anything. Eventually, I passed the point of thinking I was doing something "wrong" by doing things my way and I experimented, which led me to what I find most useful for my personal practices.
I don't use a chant or formal anything. I talk to the Deity I wish to communicate with and work with. And I don't just do it during a ritual or spell work, I do it nearly daily. I firmly believe that to successfully work with a Deity, you need to have a relationship with them and know their energy and the like. You can't just flip through a list of Deities and say, "I'm going to work with Zeus today!" without knowing anything about Him, how He works, His energy, what He finds acceptable, etc. If I wish to speak with Hekate, or work with Her energy, I simply start speaking to Her and ask Her if she would join/help me. I carry on a conversation with Her, discussing my spiritual life, how I see Her, asking Her to reveal things to me if She deems it appropriate, etc. I talk to Her like I would talk to a close friend. I don't cower at Her feet, I don't grovel, I don't command, I simply speak with Her.
I have found this method to work best for me, but I acknowledge that others have the greatest success with more formality. That's fine, too! Whatever works for you is what matters. I do suggest that you take time and experiment with different methods, to find what truly feels best. You may originally think that the way you're doing things is the right way for you, and later discover a way that's even more rewarding. You'll never know until you try.