First I suggest finding a quiet place where you can be alone and not disturbed. some people like it dark but you can meditate in the light too. Find a comfortable position of sitting or lying down. Its good to use candles and incenses to add to the mood and relax you some.
You should try to relax every part of your body, keeping a even breathing pattern (inhale for five seconds, exhale for five seconds). Let all the stress out of your muscles. Some do this with imagery by envisioning a glowing white light going through your body and relaxing your muscles. Others do this by commanding parts of their bodies to relax by words. or both.
Next you should clear your mind of any thoughts. This may take a while if you're stressed out, have racing thoughts or have trouble focusing but take your time. It may take five or ten minutes, it may take longer but if you keep focus on it you'll be able to clear your mind with practice.
Personally whenever I meditate I like to hold a stone because it gives me good energies and some crystals help with meditation and focusing the mind. I also like to gaze at a candle's flame or incense smoke to get myself into a trance. But some people can't meditate with their eyes open so they do it with their eyes shut but whatever works for you.
Try to get yourself into trance like state and dive into your spiritual mind.
then you can do imagery if you like. I do several different visions at different times. Usually I envision a rain forest with a glowing lake of silver water and go into the water to cleanse my mind and body. Sometimes i do a ladder like meditation, where I envision stepping down a ladder in the dark and going further into my mind. I also do things like beach scenes, floating in the sky or imagining myself glowing with energy.
and some people just stay in a void until they feel their mind is focused enough to come out of it.
You'll want to come out slowly, moving your fingers and toes and the rest of your body slowly to bring yourself back to the physical plane and when you're ready you can open your eyes.
there is so many different ways to meditate, just keep your eyes open and look around.