Friendship is such a blessing, that being said there's a lot that goes into a friendship. Here are a few things that are important.
Being loving is very important. You have the power to show love, to make someone else feel good, use it. If you're in any kind of relationship and they aren't being loving, for example, constantly being rude or verbal abuse. That is not being loving and you need to get out of it or confront the problem.
Above all, love each other deeply, because love covers over a multitude of sins. -1 Peter 4:8
Forgiveness is hard, but super important. You can't move forward in a relationship if you have bitterness and hold a grudge. You also do more harm to yourself than the person that hurt you. Really no one is perfect and there's going to be times where we ourselves even mess up and we'll want forgiveness as well.
And when you stand praying, if you hold anything against anyone, forgive them, so that your Father in heaven may forgive you your sins.” -Mark 11:25
An edifying friend helps you grow as a person, be an encouragement, suggests a good book, video, music, and bible verses!
Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen. -Ephesians 4:29
Honesty is key! A good friend is honest, will give their good opinion whether you like it or not, will let you know whenever you need to change your attitude, give advice on how to fix a problem, and tell you whenever you should really not eat that fifth doughnut, lol.
Pray for us. We are sure that we have a clear conscience and desire to live honorably in every way. -Hebrews 13:18
A friend that is steadfast and will stick with you through the good and bad times is one to hold on to. This goes along with forgiveness, you need to forgive to remain steadfast and not be bitter. If you're steadfast in the Lord, then being steadfast with the people in your life will come easier.
Therefore, my dear brothers and sisters, stand firm. Let nothing move you. Always give yourselves fully to the work of the Lord, because you know that your labor in the Lord is not in vain. -1 Corinthians 15:58
Be this friend.
Even if you have friends that don't have all the qualities you'd like them to have, you should try and be this friend. Everyone needs one, and who knows, you might even inspire someone to be more loving, more forgiving, more edifying, etc.