The issue is that when you try to automatically update your WordPress installation you are asked to supply your ftp login credentials. Hopefully just like me you are using unique, complex and hard to remember details. Joost De Valk created a plugin to fix the automatic update issue that some webhosts have here

The plugin (and this alternative) are a way to avoid having to go look up the details before plugging them in every time you wish to update.

In your wp-config.php you can define these values to hopefully end this problem once and for all:

define('FS_METHOD', 'ftpext');
define('FTP_BASE', '/path/to/wordpress/');
define('FTP_USER', 'username');
define('FTP_PASS', 'password');
define('FTP_HOST', 'host');
define('FTP_SSL', false);

The codex has a little more to say on the matter here

Having non-standard table prefixes can help reduce automated attacks and malicious scripts from compromising your WordPresss database

This is a fairly simple process if you are familiar with the underlying database and principles, but is not recommended unless you are experienced with queries and a sql client such as phpMyAdmin

1) Prepare by making a backup everything, redirect your visitors etc
2) Change the default table prefix in wp-config.php to your required name
3) Rename all WordPress database table prefixes

Here are the necessary SQL commands (remember to change the example to your own table prefix)

RENAME table 'wp_commentmeta' TO 'wp_rand0mstr1ng_commentmeta';
RENAME table 'wp_comments' TO 'wp_rand0mstr1ng_comments';
RENAME table 'wp_links' TO 'wp_rand0mstr1ng_links';
RENAME table 'wp_options' TO 'wp_rand0mstr1ng_options';
RENAME table 'wp_postmeta' TO 'wp_rand0mstr1ng_postmeta';
RENAME table 'wp_posts' TO 'wp_rand0mstr1ng_posts';
RENAME table 'wp_terms' TO 'wp_rand0mstr1ng_terms';
RENAME table 'wp_term_relationships' TO 'wp_rand0mstr1ng_term_relationships';
RENAME table 'wp_term_taxonomy' TO 'wp_rand0mstr1ng_term_taxonomy';
RENAME table 'wp_usermeta' TO 'wp_rand0mstr1ng_usermeta';
RENAME table 'wp_users' TO 'wp_rand0mstr1ng_users';

Remember if there are other WordPress related tables created by plugins you will need to rename these as well. ALL table prefixes should be renamed.

4) Search the options table for any instances of the old table prefixes

SELECT * FROM 'wp_rand0mstr1ng_options' WHERE 'option_name' LIKE '%wp_%'

This will return wp_user_roles and any options or configurations created by plugins or custom scripts. Update the fields as appropriate.

5) Edit the usermeta table

Search the usermeta for all instances of the old table prefixes

SELECT * FROM 'wp_rand0mstr1ng_usermeta' WHERE 'meta_key' LIKE '%wp_%'

Again these fields will need to be updated where appropriate

Test everything is working and then set your site to live once again.