No one can guarantee rankings: The success of SEO measures depends – besides the factors of your own website – also on the direct competition and mainly on Google. False or exaggerated promises are a clear indicator of a dubious approach.
References: Agencies often advertise with references from well-known companies. Here it is worth asking in detail in what capacity the agency was involved.
Case studies: Current case studies provide insight into the work. Pay attention to relevant metrics: were visitor and customer numbers increased? Were good rankings achieved?
Certificates: “Quality certificates” alone say little. Value-adding content such as blog articles, publications and podcasts underline the expertise much more clearly.
Free initial consultation: An online meeting and a short initial analysis help to assess the agency’s way of working and expertise.