How to enable clean URL in Drupal?

If you have access to server via SSH then do Check 1 and 2

Check 1: if you have access to httpd.conf then check for
LoadModule rewrite_module modules/mod_rewrite.so
and uncomment this line.

Check 2: if you have access to httpd.conf then check for

FIND SECTION BEGINNING
<Directory “/var/www/html”>
Options Indexes FollowSymLinks

AND CHANGE
AllowOverride None
TO
AllowOverride All

Order allow,deny
Allow from all
</Directory>

SAVE FILE AND THEN
# service httpd restart

Check 3: Go into your .htaccess file and uncomment
# RewriteBase /   [ It is line 101 in my .htaccess file.]

or once your hosting service enable this mod_rewrite.

Finally

In Drupal check for this path
admin/settings/clean-urls and choose to enable clean-urls here.