Drupal is a robust, highly scalable content management system, but there're some settings that often go ignored or forgotten while users are developing their Drupal website(s). I'm hoping this short list of reminders is helpful to the regular Drupaler, and that it reduces your page load times and saves your server(s) some resources.
Reduce The Bloat
Disable unnecessary modules. After installing Drupal, go to /admin/modules and check stuff like if the color module is enabled. You won't need this if you're using a template that doesn't have color configurations. Do you need statistics enabled? Google Analytics may suit you better if you're in a constrained environment. All it takes is an HTML block, place it at the bottom of your template in your blocks configuration, and paste in your Google Analytics code. You don't even need the Drupal module to do this. I still wonder why that module exists (It's a great module regardless, but still a bit redundant).
There're other useful modules, but aren't required after you're done configuring / building your Drupal website. Such modules may include the database log, syslog, and so on. These are helpful while under development, but you'll have an error_log to handle that if you're running Apache or an http handler that logs error messages to an error log.
Just to name a few that usually aren't required, the book, aggregator, dashboard, help, open id, php filter, poll, testing, and trigger modules are some you may not need. When you're done disabling / uninstalling modules, you may wish to consider deleting the modules from your /sites/all/modules and /modules directories. Save backups in case something breaks after you delete the files / folders.
You can prevent your website from stalling out by disabling cron and systematically running it via standard cron settings on your server. Go to /admin/config/system/cron and disable it on that page. Once you've done that, copy the cron URL on that page and add it into your cron scheduler. If you're using cPanel, look for the cron jobs section.
Once you have your cron URL and you're on your cron configuration area, you should call your URL like this. In this example, I'm using a cron URL of my website. (This URL is not valid, but is here to serve as an example.)
/usr/bin/wget -O - -q -t 1 http://www.larry.life/cron.php?cron_key=JrTsdRH43rWERGHER554he4
You're probably using the Drupal views module. By default, views aren't cached. Caching views does your website a world of justice in performance and scalability. Go to your views page and edit your configuration to cache views for the desired amount of cache time. You can find out if this option is disabled in /admin/structure/views/settings/advanced and configure it there. Some views often generate large queries in the database, and if you have those cached, your website won't have to make those same queries each time a page loads. Once you know your views is able to cache, go to each individual view you would like to cache and checkout the advanced settings of your view, then enable caching and choose your desired time.
Although not related to caching, you should also limit the output to a certain number of items. Not many people are going to go through all your views items, so consider reducing it to something like 5-10 per display. Use a pager. Displaying all your content at once will create unnecessary strain on your database and reduce the overall user experience. This will reduce the rendering time and memory use, as well as CPU usage of your server.
Drupal doesn't cache error pages by default. You can save your website bandwidth and your server CPU load by enabling cached 404 pages. To do this, edit your settings.php file and look for drupal_fast_404(); and un-comment that line. Make sure you read the pros and cons of enabling this feature before doing so. In most cases, it'll be fine. You won't have to install the fast 404 module if you do this, which saves you a few database queries.
Page Caching & CSS/JS Aggregation
If most of your content is static, you can also enable "Cache pages for anonymous users" and enjoy the benefits of speed often seen in static HTML websites. Your caches will periodically flush, but they'll be rebuilt after a preset time frame you configure in your performance settings.
I hope you found this article helpful. It contains information I feel most Drupal users and developers often overlook while building / developing their Drupal website(s). These are the first things I do when I build a Drupal website, and it will be advantageous if you did this as well. You'll save bandwidth, CPU, and RAM by doing the above.