A good friend,I think,he should be a friend in need.He will not leave you alone when you are in trouble.
On the one hand,we should be kind to our friends.when our friends are in trouble,we should try our best to comfort them.what is more,we are expected to help them to solve problems.So our friends will not feel worried any more.
On the other hand,we should be strict with our friends.when friends make mistakes,we can ask them to correct on time.Therefore,they will not make bigger mistakes.This is what a friend should do.
In a word,good friends should to be heart-to-heart forever.