Digital marketing is a category where the sales process and the actual service are, ironically, easy to confuse. An agency's own website, case studies, and pitch deck are marketing artifacts, produced by people whose job is persuasion. That is worth remembering while evaluating one.
Results without context are not results
"We grew a client's traffic 300%" means very little without the starting point, the timeframe, and what else changed for that client during the period. A small account growing off a near-zero base looks dramatic in a case study and proves almost nothing about what the agency can do for an established business with an established audience. Ask for the baseline numbers, not just the percentage.
Who is actually doing the work
Many agencies sell the founder or a senior strategist in the pitch meeting, then hand the account to a junior team once the contract is signed. That is not necessarily wrong, but it is worth knowing upfront. Ask specifically who will be on the account day to day, and ask to meet them before signing, not after.
Reporting cadence reveals more than the proposal does
A proposal describes what an agency intends to do. The reporting cadence they propose describes how accountable they expect to be held. Agencies confident in their results tend to offer frequent, specific reporting without being asked twice. Agencies that hedge toward quarterly summaries and broad narrative updates are often managing expectations rather than managing performance.
The pattern underneath all of this
None of these red flags are visible in a first meeting. They surface in reference calls with actual clients, in a close read of case studies rather than a skim, and in direct questions the agency has to answer without a script. That is exactly the work that gets compressed, or skipped, under deadline pressure, which is when a marketing vendor decision is most likely to go wrong.