If you make contact with an angel (or angels) during prayer or meditation, it's important to determine whether or not the spirit(s) is truly your guardian angel or other holy angels whom God has assigned to watch over you.
That's because the act of praying or meditating to an angel (rather than directly to God) can open spiritual doors through which any angel may choose to enter. Just as you would check out the identity of any person entering your home, it's important to check out the identity of any angel entering your presence, for your own protection. Many people believe that testing the angelic presence who responds to you is crucial to protect yourself from fallen angels who deceive people by pretending to be holy angels, but who actually have bad intentions toward you -- in contrast to the good purposes that guardian angels want to fulfill in your life.
You don't need to worry that your guardian angel will be offended by your request to confirm his or her identity. If it's really your guardian angel who is visiting you, the angel will be glad that you asked for confirmation, because one of your guardian angel's main jobs is to help protect you from harm.
What to Ask
You can ask the angel to give you a sign that is meaningful to you in your faith -- something that will help show you more about the angel's purposes for communicating with you. It's important to ask the angel some questions, as well, such as what the angel believes about God and why. That will help you discern whether or not the angel's beliefs line up with your own.
If the angel or angels give you a message of some kind, you should also test that message rather than automatically assuming that it's true. Examine the message to see if it really is consistent with what you know to be true in your faith and what your sacred scriptures tell you. For example, if you're a Christian, you can follow the Bible's advice from 1 John 4:1-2: "Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world. This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God."
A Sense of Peace
Keep in mind that you should feel a sense of peace in the presence of your guardian angel. If you feel troubled or upset in any way (such as experiencing anxiety, shame, or agitation), that's a sign that the angel communicating with you is not truly your guardian angel. Remember that your guardian angel loves you deeply and wants to bless you -- not upset you.
Once You Discern Identity
If the angel isn't actually a holy angel, respond by confidently telling it to leave, and then pray directly to God, asking him to protect you from deception.
If the angel is your guardian angel or another holy angel who watches over you, thank the angel and continue your conversation in prayer or meditation.