Hello CE User
I see this question all of the time in reviews for extensions, so there must be many that do not know about a standard way to install Extensions!
Always for me I turn compilation off (I don't use it, as it makes my FPC run slow), install, flush the Magento cache and/or Java/CSS, and log out and in, but I think most miss flushing the browser cache as well and if you use it like on mine APC and Memcache(d), Da-Bomb, no 404 error!!!
To flush the Memcache(d) you can do this via SSH CLI or putty. This assumes you know how to login to your server! For me it is done in Linux Terminal; [ssh root@my_IP_address] and then password. This should put you at the root of your server. If not then issue the command [CD ~] Mine then reads root@vps8000 [~]#, some may end in $ or other symbols. When copying from someones post leave off the # or $ as I did in the next text.
telnet localhost 11211
flush_all
quit
I have a nice little extension for APC:
http://connect20.magentocommerce.com/community/Speroteck_ApcClean
I don't know if it is still avalible on Magento connect?, but is is on Google
