The choice shouldn't be based solely on price, the positions the agency promises, or the number of services it lists. It's advisable to check if the agency has verifiable experience, success stories, public reviews, and credentials related to the platforms it manages. It's also important to know who will be executing the project and how the different specialties will coordinate.
A clear proposal should explain the initial diagnosis, objectives, scope, deliverables, responsible parties, monitoring methodology, and the key performance indicators (KPIs) that will be used. For Google Ads, it should include a review of current metrics and conversions. For SEO, it should differentiate between technical, semantic, content, and authority-related actions.
It's also advisable to avoid agencies that guarantee top Google rankings, a fixed return on investment, or exact results within a specific timeframe. Performance depends on factors such as competition, budget, offer, website, market, and the quality of the measurement.