I've been working with the same Spirit for about ten years now. So. Speaking from personal experience and reading/study?

Through Journeys. That's how I've met all my spirits, and that's the easiest way to talk to them, and talk to them clearly.

It's a hybrid of a meditation and a dream, half way between waking and sleeping. That's the best way I can think to explain it.

Drumming. Meditate. Visualize. Try not to overthink it.

For an Underworld Journey, you visualize yourself descending into a hole of some capacity. A cave. A hole amongst a trees roots. Whatever. What matters is that you are going down into a world bellow.

For an Overworld Journey, you visualize yourself ascending up something. A ladder. A rope. A mountain. Whatever. What matters is that you are going up into a world above.

Don't associate Over and Under with Good and Evil. That's not quite it. They're different journeys, but it's not a matter of "The Good World" and "The Evil World", the same spirit has met me in both.

Once you are there, you seek your Spirit. You can ask them various questions if you want. I've heard some people say you should ask them "Are you from the Creator" three or four times.

The first question I asked my spirit is "Are you a Spiritual Being, or a projection of my psyche?"

It's answer was "Oh. Wow. What a big question. Probably a projection of your psyche."

I actually had a far more intense journey than I ever had before quite recently. I connected with my spirits far more deeply than I usually do. They declared in no uncertain terms that they are Me. Projections of my Psyche.

Interestingly enough, one of the most potent journeys I have done was the single Journey I have done on behalf of another person. My spirits were there, but they were 'observing' and it was clear the other person's spirits were 'in charge.' They withheld information from me that they 'did not want me to know', and I was booted from the vision when they told me 'what they wanted me to pass on.'

I don't care if you believe in Spiritual Beings, or aspects of your Self. It sounds like you are seeking the experience?

Anyways.

Don't worry if you aren't opening your eyes and finding yourself in a magical, new world, like the "vision Quest" episode in some corny cartoon. My journeys have often felt like high quality shadow puppet shows.