There's a host of things you need to think about when designing an archaeological survey, as well as to assess a survey's results. This video covers many of the factors that can affect the effectiveness of a survey, including visibility, characteristics of targets (sites or artifacts) and detectors (including humans), and the geometry of sampling units or search patterns. It is not exhaustive, but covers many of them. It also discusses briefly the detection functions that mathematically summarize many of these effects, and how they contribute to Sweep Width, which is an important element in estimating survey coverage. Coverage, in turn, is the simplest and most useful measure of survey thoroughness.
One thing I noticed on reviewing the video is that I misspoke about the difference between intensity and coverage. Intensity just measures how much effort the survey expended in the surveyed space (e.g., person-hours per hectare), irrespective of how successful the search was. Coverage takes into account the effectiveness of the surveyors; the exact same amount of effort (intensity) in an area of poor visibility has less coverage than in an area of excellent visibility. For fieldwalking and some other methods, we extablish this with the difference in sweep width. Where transects have wider sweep width, they cover more area.

For more on this topic:
Quality Assurance in Archaeological Survey https://link.springer.com/article/10....

Archaeological Survey https://link.springer.com/book/10.100...