You can use this query to find the table information:

SELECT
  a.attnum,
  a.attname AS field,
  t.typname AS type,
  a.attlen AS length,
  a.atttypmod AS lengthvar,
  a.attnotnull AS notnull
FROM
  pg_class c,
  pg_attribute a,
  pg_type t
WHERE
  c.relname = 'your_table_name'
  AND a.attnum > 0
  AND a.attrelid = c.oid
  AND a.atttypid = t.oid
  ORDER BY a.attnum

Use the following query to show all tables without primary keys:

SELECT
  nspname AS schema,
  relname AS table
FROM pg_class
  LEFT JOIN pg_constraint ON
    pg_constraint.contype = 'p' AND
    conrelid = pg_class.oid
  JOIN pg_namespace ON
    pg_namespace.oid = pg_class.relnamespace
WHERE
  relkind = 'r' AND contype IS NULL;

Given a table MYTABLE in namespace MYNAMESPACE, you can use this SQL to retrieve the primary key column name(s) for the table:

SELECT
  attname::text
FROM
  pg_attribute
JOIN
  pg_class ON pg_attribute.attrelid = pg_class.oid
JOIN
  pg_namespace ON pg_namespace.oid = pg_class.relnamespace
LEFT JOIN
  pg_constraint ON conrelid = pg_class.oid AND pg_constraint.contype = 'p'
WHERE
  pg_namespace.nspname = 'MYNAMESPACE' AND
  pg_class.relname = 'MYTABLE' AND
  pg_attribute.attnum = ANY (pg_constraint.conkey)
ORDER BY
  pg_attribute.attnum;

If you have a database mytemplate that you'd like to use as a template, update its datistemplate attribute in the pg_database relation:

UPDATE pg_database SET datistemplate = 't' WHERE datname = 'mytemplate';

Then you can use it as a template when creating other databases:

CREATE DATABASE otherdb TEMPLATE mytemplate;