How to list all of a table's indices
Remember, the easy way, when you are in psql, is to just do
\d mytableand look for the "Indexes" portion of the table description. Otherwise...
  select t.relname as table_name,
         i.relname as index_name
    from pg_class as i
    join pg_index as idxjoin
      on i.oid = idxjoin.indexrelid
    join pg_class as t
      on idxjoin.indrelid = t.oid
   where t.relname = 'my_table'
     and i.relkind = 'i'
order by t.relname,
         i.relname;