So, this is a question asked around here a lot, so I thought I would share one of the methods that were useful for me. A friend of mine made it, so I am posting it here, with her permission.
Begin by humming "Mmmmmm", and don't worry about pitch or tone. It is good to have your arms stretched, not in the sign of a cross, but in the sign of an arrow so to speak, with 45 degree angles, like this:
Now, the Greek letter psi.
Take that image, and gaze into it softly, as though you are looking into, or looking through the sign. Gaze carefully at the centre, where the arms of the psi are resting. The key is to have a retinal after-image and see psi at the back of your mind even when your eyes are closed.
CLose your eyes, changing the MMM vibrations to IIII(like ''aye'' stretched out, not like eee).
Bring your hands to your sternum, or wherever it is you feel the center of your body is, in your heart, around your waist, etc. and see the Psi morph into the Norse rune, Algiz.
Keep looking at it, while saying "Iiiii" ("eye") - it might double or change, what you need to do is focus on bringing it in your closed-eye vision to a place where you?re slightly cross-eyed - like someone holding it just in front of you.
Look for a diamond, or a shape like a grain of rice but with pointed ends, in the place where the Y-arms of the Rune meet.
It will shine, either violet, or blue or white. Doesn't matter, but it is bright. Literally the centre of the rune.
Breath it in, through your brow, into your Ajna chakra. It may land elsewhere, like on your nose or hairline. Don't dismiss it, even if you can't see it all in the first few tries. Persist.
At that point, when it is done you may want to focus on that chakra and simply relax, using your breath to mediate the energy that's flowing through it and using it for whatever it is you are opening your Ajna chakra to do.
Once again, this method came from a friend, it worked for me, I am just posting so others can have something else to draw from.