Once you have decided to move to the cloud environment, the first step you must do to select a cloud provider. There are plenty of them in the market but not all will suit your requirements.
Discuss your business objectives with the service providers, make sure they understand what you require and can converse in the same tone in terms of your objectives. You must listen to what they plan, promise to do. Up-time, speed, support are common goals every provider talks about. Try to understand what they say how unique they are and why you must use them. How you will benefit from their services.
Where are the data centers located? How secure will your data be? It should be somewhere close to where your audiences are. You need providers that are available at multiple locations and can deliver your services without issues like network availability, latency, up-time cropping up.
The providers must follow the security architecture laid out by the Cloud Security Alliance(CSA) and British Standards Institution(BSI) and receive certification. View their track record about issues that occurred previously and how it was handled.
Another important point is the exit planning. You must not get into a lock-in situation. Negotiate about the consequences, penalties, if you want to exit midway.
Cost is important. Compare costs but remember quality comes at a price. You cannot get anything free or cheap. If quality is retained, you can recover your investments better so, never let cost be a deciding factor when choosing a cloud service provider.