Don’t be jealous. Or if you are, just admit it and get over it. Jealousy has a way of turning into bitterness which develops into a quiet resentment. It’s a slippery slope that can ruin your relationship if not caught and quarantined.
Talk. Be a good communicator. It doesn’t matter if you’re making dinner plans or being honest about hurt feelings. Good friends talk to each other and share their hearts.
Listen. Stop if it feels like you’re talking too much about yourself. Ask them about their day. Rejoice with them when things are going well. When things are rough, be there for them and stay there until the tears have dried. Give space if asked for it. Simply put, listen to your friend.
Help. Friends help friends. Whether it’s moving or baby-sitting, a good friend will lighten your load and you should do the same (within reason and balance, of course, but we’ll get to boundaries later)
Here are some great Beliefnet features on friendship.