Most organisations shortlist partners on price and Microsoft credentials. Both matter, but neither predicts whether the implementation will go well. The stronger signals are industry familiarity, the seniority of the people who will actually be on your project, and how the partner behaves when you push back.
Ask who is delivering the work, not who is selling it. It is common for an experienced consultant to run the sales conversation and a much more junior team to deliver the project. Ask for the names, the split of their time, and whether the consultant in the room will still be involved at go-live.
Ask for references in your sector and at your size. A partner with deep manufacturing experience may be an awkward fit for a professional services firm billing time against projects, and a partner used to 200-user enterprises will often price and staff a 15-user rollout badly. Sector fit shows up in how quickly they understand your process without you having to explain it.
Ask what they would not do. A partner willing to tell you that a requested customisation is a bad idea, or that a standard Business Central process should replace one of your existing workarounds, is usually the one that keeps your total cost of ownership down. Partners who agree to everything tend to build expensive, fragile systems.
Finally, look at what happens after go-live. Ask about the support model, response times, who you contact, whether support hours roll over, and how release-wave updates are tested. Support is where most of the relationship lives, and it is the part most often glossed over during the sales process.