I had problems with editing the php.ini file because with most webhosts it is globally and inaccessable for us and you still would have to add a line in .htaccess anyway.
However, I found an easier way if you have access to the .htaccess file in your www folder. Just include the following 2 lines in .htaccess:
php_value upload_max_filesize 20M
php_value post_max_size 20M
For changing the memory limit add/edit this in .htaccess:
php_value memory_limit 20M
And of course change the 20 to anything you need.
Or you can follow the steps at wptheming – http://wptheming.com/2009/07/upload_max_filesize if the above does not work.
Jim Callender is a Freelance Wordpress Developer. Living & working in Brighton. He started working with Wordpress in 2003. Since then has been responsible for delivering high profile sites for a number of large UK design & marketing agencies. His other site is www.jayonline.co.uk