Stay in contact.
Keep in touch.
Find the same things funny.
Have the same sense of humour.
Like/enjoy the same things.
Have a lot in common.
Not stay in contact.
Lose touch.
Know somebody better.
Get to know somebody.
Like to be with somebody.
Enjoy somebody's company.
Stop being friends.
Fall out.
Make friends.
Fall in.
Understand each other well.
Be on the same wavelength.
A person one knows slightly, but who is not a close friend.
An acquaintance.
