Before you head into any discussion with a new OEMS or EMS provider, make sure to have these talking points ready prior to the demo. That process helps manage mutual expectations for pricing and service requirements.

What are your current pain points with your current EMS provider?
Think of your current workflow and identify what is preventing growth, what could be done more efficiently, and what steps can, or should, be automated by your OEMS provider.
A summary of your end-to-end workflow
Think of the full lifecycle of your order flow, starting at where and how the order originates all the way to when it gets executed. Also, identify any other systems or processes need to know the order details as well (e.g. clearing firm, position monitor, margin engine, etc…). Map this lifecycle out and have it ready.
What, if any, third party integrations / systems do you need to be tied into your EMS or OMS solution set?
Similar to the point above where you identify other systems or processes that need order data; think of all the end-points that require your trade data and also identify whether that is a real-time requirement, or if file based transmissions are adequate.
Turn around time: When does this need to happen?
Identify when you need to be live and operational on the new OEMS solution. This may be dictated by new workflows coming online, existing vendors sunsetting their products, or a specific live date requirement for any other reason. It’s important to communicate this timeline to the vendor and ensure they can meet or beat that deadline, else you may run into lost time and revenue.
How are you clearing trades today?
There are many different ways in which trade flows can be cleared and settled, some are more sophisticated than others. You should have a solid understanding of your clearing needs and explicitly state them to any vendor you are shopping to ensure they can cover the workflow requirements.