You can use all the ingredients, say all the words, and make all the motions a spell or ritual calls for, but if you cannot alter your state of consciousness you will not have a strong effect upon the world around you. Achieving such a state honestly is not as easy as it may seem. Where some people can easily use a guided meditation, others might need other means to do such. There can never be "one true way" of bridging the worlds.
Most Witches come to the understanding of consciousness-shifting via the Eight means mentioned by Gerald B. Gardner (founder of Gardnerian Wicca), but I learned about 12 Gateways to Power via Christopher Penczak (Temple of Witchcraft Tradition). Utilizing as many of these can assuredly help you achieve this state.
Our Conscious Mind does not like not being in control. When we attempt to alter our state of consciousness, it fights back. Thus it is important to learn to train your Middle Self to let go.
One means of doing this, and it seems the most boring, is to Countdown.
Begin by getting physically relaxed by whatever means you utilize. Close your eyes. And then, on the Screen of your Mind, visualize a set of numbers appearing. Begin with 12, counting down to 1. If you cant visualize the number, practice can help. Take your hand or mentally see yourself drawing the number. Focus on each number, knowing that the number is there.
If you break concentration, start over.
If you can maintain that. Try a higher number. The goal is to reach 100. This trains the mind to hold this focus for a long period of time.
Many are there who can achieve an altered state, but cant maintain it when they absolutely need it.
I will be creating video guides to do this here soon. They will be part of my upcoming course on developing psychic abilities.