if your host allows you to overwrite apache conf through your .htaccess files, you can already make some basic configuration that have a efficient impact on your page loads (some of them are already included in the magento .htaccess.sample file).
Check more on http://developer.yahoo.com/performance/rules.html
Exemple for apache 2 conf :
- Enable expires header and disable ETag:
# Set expiration information only for scripts and stylesheets
# Enables generation of 'Expires' and 'Cache-Control' headers
# Sets default expiration time
ExpiresDefault "access plus 10 years"
# Disables entity tags (ETags)
- Enable gzip compression :
AddOutputFilterByType DEFLATE application/json
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/xml
Does anyone know more about making some more low level optimization : more caching, db , apc ??