An example of view block with related nodes based on 'tags'.
1. Create a block (take a look at screenshots below)
2. Add a relationship: Taxonomy term: Content using: Tags
3. Add contextual filter: (field_tags) Content: Nid
When the filter value is NOT available
Provide default value -> Content ID from URL
this contextual filter will remove current node from the view
4. Add contextual filter: Taxonomy term: Term ID