to answer your question, you can either edit php.ini or use .htaccess as you have read.
to edit php.ini, first find out where it resides by viewing the output of this file via HTTP:
once you know where it is, you can edit it using vim:
(i believe pico and nano are available alternatives as well)
while in vim, type this in to search for the register_globals directive:
= escape key
the + signs are not literal. they just imply that you have to use a key combination
hit "n" to repeat the search.
once you've found register_globals, hit "i" to go into insert mode to enter text, change its value to "on". it should be "off".
now save and exit the document like this:
now for these changes to take place, you would have to restart apache because php.ini is parsed only once at startup. i doubt we are allowed to do that (i'm new to dreamhost, this is my first day)
the following is the .htaccess solution (i'm assuming you have php4):
php_flag register_globals on
For further reference: How to change configuration settings
having said all that, avoid using register_globals. it can lead to many security issues and it's truly not worth it because depending on if the variables have been thoroughly initialized and the nature of the code, your entire site/database can be wiped out.