Mobile phone with GPS and compass support (or take your own compass and hand held GPS device).
OS Map to record the location (back up if signal is poor for mobile GPS).
x 10 hand lens as some lichen features are small.
Identify five oak or five birch trees (not a mixture of the two) growing under similar environmental conditions (not densely planted or shaded).
Trees that are covered in ivy should not be used.
Trees should be single stemmed (standard) with a straight trunk, > 40 cm in girth.
Look for availability / accessibility of branches.
Avoid sites on calcareous soils. Determine the calcium carbonate (CaCO3) soil levels in your location at this website.