Expect to disagree. Develop a healthy mechanism for ironing out differences, or you will be getting together only when things go wrong. It won't last if it's just built from the top. It's important to recognize and acknowledge early on the strengths of the medium of each partner. To the extent the partners have flexibility, assign maintenance of the partnership to staffers who enjoy building consensus.
Individual relationships make or break partnerships.
When turnover happens, expect a few lumps in the gravy and don't live in the past. Compatibility Matters Start with respect, then build trust. Compatible editorial viewpoints count. Sometimes it's poll results. Sometimes it's an event.