When you want to install or upgrade a plugin, WordPress will most probably display this message:

Connection Information

To perform the requested action, WordPress needs to access your web server. Please enter your FTP credentials to proceed. If you do not remember your credentials, you should contact your web host.

If you are on shared hosting you might not have this problem but if you are on a VPS or Dedicated server you will most probably get asked to supply FTP credentials every time you want to install or upgrade plugin or even WordPress. This can become an annoyance if you install plugins a lot so this is one of the first things I always fix when I install new WordPress site.

Here is how to solve it: open your wp-config.php file (by default it can be found in your root WordPress directory) with text editor and simply add your ftp login information near the bottom of the wp-config.php file (just above the /** Sets up WordPress vars and included files. */ comment for example):

//*add your FTP credentials*
define('FTP_HOST', 'host_IP_or_FTP_url');
define('FTP_USER', 'FTP_username');
define('FTP_PASS', 'FTP_password');
//*If you like and can use a SSL connection set this to true*
define('FTP_SSL', true);

After you do this your won’t be asked for FTP credentials anymore. There are other solutions like settings permission with chown via shell or installing suPHP on your server but this one seems to be the easiest.

If the above fails for whatever reason you can comment the above code and try adding the following code in the wp-config.php file,somewhere at the top:

define( 'FS_METHOD', 'direct' );
define( 'FS_CHMOD_DIR', 0777 );
define( 'FS_CHMOD_FILE', 0777 );

This forces files to be writable by the server. You should only use this if adding FTP credentials method fails.