We know which angels are with us through the discerning of spirits.  Just as you pick up on the demonic that is around you by your spirit man so also you can discern which angels are present and around you to minister to you.  When you are depressed you may discern a spirit of hope around you who will speak to you words of hope and scriptures of hope.  There may be a spirit of joy that comes to minister to you and these angels show up in worship and when they minister to people the people start laughing.