Good indexes?

index.sql

SELECT p.content, u.name
FROM posts p, admins a, users u
WHERE
  p.tag = a.tag and 
  a.id = u.id and 
  p.content = 'Hello World';

SELECT u.name, p.date
FROM users u, posts p
WHERE
  u.userid = p.userid and 
  p.content = 'Hello World';