The quote below is the advice that the Lord Buddha gave to young man, Sigala.

“A son of a good family should look after his friends and companions in five respects:
by being generous,
by talking kindly,
by acting helpfully,
by treating them equally,
by not breaking his promise.

When a son of a good family looks after his friends and companions in these five respects, then they show him sympathy in five respects:

they look after him when he is reckless,
they look after his belongings when he is reckless,
they are a comfort when he is afraid,
they do not abandon him in times of trouble,
they honour his descendants.

When a son of a good family looks after his friends and companions in these five respects, then they show him sympathy in these five respects, and in this way the north is covered by him and kept safe from danger.”

From the collection of Long Sayings, Advice to Sigala.

Many teaching of the Buddha emphasise on friends. Only the Lord Buddha himself can be self-enlightened, others need good friends (Kalayanamitra) to guide them to the right path.

There are two factors that are prerequisite to the Ariya Magga (the Noble Eightfold Path), They are 1. yoniso-manasikara (Mental attitude toward environment) 2. Kalyanamitta (Influence from a good social environment and good social relationships dhamma) or the other word; 1. internal factor and, 2. external factor.

The internal factor is accumulated from your past (include past lives), the self improvement that you make in many little steps during the time. The external factor will help to reinforce your direction, your improvement or it could have an effect in the negative way depend on the environment, good or bad friends.

In practical, it is impossible to find a perfect one. We only associate with people who are developing themselves, some of whom might do better than others. So we have to be able to choose the right one to follow and avoid the bad influence of others. If we develop ourselves well enough, we can help our friends to change their bad behaviour as well. In order to do this, we must use our wisdom to find the way to influence them to change.

Temple would be the best place to start the process as people come to the temple with the intention of improving themselves. They are ready to take advice from the teaching monks. The monks, who we sometimes call Ajahn, will take his duty to examine us like doctors examine their patients and with his kindness, selects the right teaching to help us to improve ourselves. All the friends we met at the temple would do the same and we will reinforce each other for the development. Once we better ourselves and have more confidence with the practice we can be a good example for people around us at home or at work. For example, if we focus in practicing loving kindness,  we will always be looking for what we can do to help others. When giving is not necessary that it has to be gifts or money. It can be as simple as smiling to others, giving advice or encouraging words. It is the way to show people that we care.