The problem with pitch presentations is not that people are dishonest. It is that a group in a room always starts listening to each other, and whoever speaks first colours the rest.
The three rules that fix the most
1. Fix the grid and the weights before the first presentation. Five axes are enough: the work, the team, the fit, the price per unit of work and the stability. Anyone assigning weight afterwards assigns it to the axis where their favourite happened to be strongest, and nobody does that on purpose.
2. Have everyone score alone, right after the presentation and before the discussion. On paper or in a form, without consultation. Only then talk. This is the cheapest intervention on this entire list and the most effective.
3. Discuss the differences, not the average. The two assessors furthest apart saw something the others missed. That conversation is worth more than a ranking.
What to watch
The order. The agency presenting first sets the yardstick; the last one lingers best. Schedule the three as close together as possible, ideally on one day, and keep ten minutes of silence after each presentation for scoring.
The presenter. Presentation skill is a real skill and it counts, but it is not the skill you are buying. After a strong presentation, ask yourself whether the substance would be as strong on paper.
The presence of the people who would do the work. If the presentation is carried by someone who then disappears, you are assessing a salesperson.
Two things to ask in advance
Ask every agency to deliver its proposal in writing as well, by the day before at the latest. Everyone can then read it without a voice and without animation, and that makes a difference.
And ask for the same sections in the same order: approach, proposal, team, planning, price. Comparing three proposals in three structures costs you half a day and produces a feeling rather than a judgement.
An independent chair helps more here than a better form: someone who guards the grid and has no stake in the outcome. That is the role IKAg plays in Agency selection & pitches.
See also: which criteria to use and how to compare two agencies.