So, you don’t agree with the Boss?
The more at ease you are in relationship, the easier it is to raise issues. When there is a buffer of goodwill, security in the situation, positive history.
But that’s not your situation.
If it was, you would not have this issue.
What is it you want to happen here? And why do you want that, really?
Is it relevant to an issue, or the person?
Are you disagreeing about the goal or just the way to get to the goal?
What is at stake?
What matters to your Boss?
How can you add value? Who can you team up with to influence?
Do your preparation. Be sure of your ground. Have the data.
Questions are your friend because: selling isn’t telling. Selling is searching for their perspective, understanding their needs, experience, priorities, contextual considerations. Be curious about their thoughts, needs, priorities and motivations before you sell/tell yours.
Raise your idea in the context of how to meet these needs. Package it as a way to solve their problems. Wrap it by relating to their experience. Focus on the benefits – avoid a power play. Can you run a trial, a test, an experiment?
Ask for something. Often, a big request declined, can then result in a smaller request agreed.