That all depends on you and the brief. It is important to be personable and easy to get on with people so that your arrival does not cause waves but similarly you need to project your expert status and your knowledge instantly so that you can get the job done.
One thing that is key is around processes. As you will discover below, most agencies have their own processes that you will have to work with so don’t be too wed to your ways of doing things if working as part of another agency. Do inform and advance their way of doing things with your own thinking but never sign over your tools to them as these are how you will be selling yourself later down the line.