What is htaccess and How to Use It?

Force HTTPS

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

Disable Directory Listing

Options -Indexes

Custom Error Pages

ErrorDocument 404 /404.html
ErrorDocument 500 /500.html

Protect wp-config.php

<Files wp-config.php>
Order Allow,Deny
Deny from all
</Files>