I'm not an expert but the basic method is to sit in a darkened room, have a lit candle (or the light of the moon) near the scrying mirror. Meditate for a few minutes to calm your mind. Then gaze into the mirror, unfocus your eyes and let your mind be open to any visions you see. You will have to interpret any symbols you see. It is similar to crystal ball gazing. You are letting the unconscious mind show you things.
Hope this helps.
In a nutshell: First, you should be well versed in casting a circle or opening a temple, banishing and being able to go into altered states of consciousness. You should also have some knowledge of who or what you want to scry. Prepare invocations of the entity you want to scry or meditations if it is a location. It would probably be a good idea to record these and be able to have them loop so that they can play while you go into your altered state. Also, it is a good idea to have something to record your experience. You should have a pair of candles that you can hold while gazing into the mirror. The color of them should be appropriate to what you are trying to scry.
Begin with opening the circle or temple. Always make sure to clear and protect yourself while doing these types of operations. The mirror should be outside of the circle, and can also be placed with a circle or triangle to restrain whatever is being called if you think it necessary. Go into your altered state and begin playing the loop you recorded. Let it continue as you gaze into the mirror. You should be holding the candles at either side of your head so that they chine on the mirror, making it a little more difficult to see any reflection. Allow the recording to play, letting the words move through you until you see the object of your scrying take form in the mirror, then stop the loop. Ask whatever questions you have for the entity or observe where ever you are scrying. Record what you see or hear. When completed, release the entity (if any) and completely banish and clear the area. Close the temple or circle.
You should never just "open up" to see what happens with scrying. It should be done with intention and purpose and not taken lightly. Obviously, this is a large and complex operation. That is why it is most often done with two people. One being the scryer and the other to do the invocations, ask questions and record answers. If you are not familiar with the basics of magic or have little practice in the elements of ritual and magical practice it would be prudent to put off scrying until you do.
Are you asking if you can find a spell off this page, do it and it will work? Probably not. Now, if you are asking if, once you have learned the basics and developed the proper abilities and experience if scrying will work then the answer is yes. Perhaps you should be more specific with your question.