close #1: this is how you may display categories and tags on a page

layouts/_default/single.html

@@ -3,6 +3,13 @@
 <h1><span class="title">{{ .Title }}</span></h1>
 {{ with .Params.author }}<h2 class="author">{{ . }}</h2>{{ end }}
 {{ if (gt .Params.date 0) }}<h2 class="date">{{ .Date.Format "2006/01/02" }}</h2>{{ end }}
+<p class="terms">
+  {{ range $i := (slice "categories" "tags") }}
+  {{ with ($.Param $i) }}
+  {{ $i | title }}: {{ range $k := . }}<a href="{{ relURL (print "/" $i "/" $k | urlize) }}">{{$k}}</a> {{ end }}
+  {{ end }}
+  {{ end }}
+</p>
 </div>
 
 <main>