Speak to each other directly
Solution-centered, the manager expresses clearly what he/she wants, what he/she likes and what is not suitable. To get to the latter, a more difficult one, the structure «I see, I want» goes straight to the point and avoids awkward twists and turns. In this case, the manager takes care of what is not appropriate with courage and transparency, and what he/she wants to facilitate action (he/she avoids expressing what he/she does not want because the brain does not integrate negation). 
The message is delivered in a calm and safe way, focusing on facts.

Speak to each other with consideration
Consideration facilitates direct communication. It induces politeness, tact, kindness and empathy without any judgement. Consideration thus balances the requirement for direct communication through a gentler opening to the other. Contrary to what is often written, consideration does not mobilise a specific strategy depending on people, but rather a self-focus and our own needs as well as accepting differences. Thus, to gain consideration, the manager expresses his/her truth while being aware that the employee has his/her own and as such is ready to listen.

Address problems as soon as possible
Human relationship problems are driven by the complexity of people involved and the fact it is difficult to understand the interactions that will take place. Not intervening means taking the risk of chain reactions with wider consequences. Any problem must be dealt with as soon as possible, as long as emotions do not compromise good interactions. If necessary, the manager takes the time to regain serenity and sufficient lucidity to deal with the situation.

Adopt the law of benevolent interference: it is the first who sees who speaks
Any person must be able to intervene on a deviation of a third party, beyond respect of hierarchical rules. For safety matters, this is obvious that anyone must intervene with a person who puts him/herself or others in danger. However, it remains true for any other kind of issue. Nevertheless, as mentioned above, it is necessary to use tact and precautions: “I have the impression that... It seems to me that we should... am I wrong?”. It is also important to prepare your answer to the rejection reaction from a person who would not understand the injunction of someone who is not their leader: “OK, in any case, what is important for me is to warn you...”. If the deviation is significant, his/her N+1 is notified that an intervention has been done.

Address problems in all their dimensions, especially regarding the relationship
When two employees argue over a box of masks that has not been filled, the problem is undoubtedly due to a protocol not being respected, but also and above all, due to a degraded relationship, without which there would have been no dispute, and it is indeed this root cause that we must confront. Nevertheless, identifying a degraded relationship is interpretative and requires developing a message imbued with tact, otherwise it could be taken for a negative judgment: I have the impression that the problem is elsewhere. Maybe I’m wrong, but it seems to me that...”.

Prohibit any e-mail containing a tension or a dispute
Relational issues are handled live or by phone, never via email. Emails can cause misunderstandings and devastating email returns. If we put in perspective the effectiveness of these types of electronic exchange, in relation to the time allocated to their formalization, the efficiency is almost zero and the collateral damage real. If necessary, an e-mail can be used to trace the exchanges. Faced with a devastating mail, you can also write: “I think we should talk about it, I call you” (with copy to all those who were already copied in previous mails).

Share your reference with your collective
The principles discussed above are relayed to the team or group as regularly as possible to facilitate their adoption. The manager looks back at recent discrepancies (without ever mentioning the employees involved) and asks his/her team members about the behaviors to adopt so as not to have to repeat the same observation. He/She asks repeatedly, “Talk to yourself!” When a colleague comes to complain about his/her colleague, the recommendation remains the same.