Ask what they really do
Some suppliers own stock and manage imports. Some act as brokers. Some understand CRT registration and UK manufacturing. Others only arrange the liquid.
None of those models is automatically wrong, but you need to know who is accountable for each part of the job.
Get a proper specification
Agree agave percentage, class, ABV, sensory profile, analytical limits, packaging format, batch documentation and acceptable tolerances.
A sample is not a specification. It is a starting point for one.
Test the service before scale
Pay attention to how clearly the supplier answers questions, how quickly documents arrive and whether timelines are realistic.
If communication is vague during sampling, it rarely improves when a container is on the water.
Think beyond the first order
Ask about production capacity, lead times, forecast commitments and what happens if your demand grows quickly.
A good supplier should help you build a route that works now without creating a completely different problem at the next stage.