Do you know who your friends are?
When organising a day out with your friends, consider a team building day. There are several designed for businesses. Look them up in your area. What strengths do your friends really have? Who works well under pressure? Who can think outside of the box. Who is a REAL team player?
Making friends is relatively easy, maintaining platonic friendships takes work, just like any other relationship. With a group of about 6 friends, agree a sum of money and put it into a pot, add to it on a weekly basis. When you have enough book a team building day and go off and get to know each other.