You should establish performance goals to ensure you spend effort wisely. These tips will help:
Measure your site performance to establish a performance baseline
Define goals and requirements for your site or application
Review the data you have to find the most important areas to improve
Define a list of potential improvements, categorise them by effort and impact, and prioritise the improvements that will bring you closer to your goals
Cautiously build the site and ensure your architecture doesn't impact the performance
Select the modules carefully to avoid performance issues
Establishing a performance baseline
Before attempting performance tuning, establish a performance baseline. Having the baseline will help you to assess how much of an improvement is achieved during and after the optimisation.
Once your website is running publicly, you need to use an external speed optimisation tool like http://webpagetest.org/. Make sure you select the closest test location - for example, consider running your test from a data centre in Sydney.
An external performance analysis tool allows the following metrics to be captured:
First Byte Time
Document complete time
Fully loaded time
Number of requests
These are the metrics that we can control on the application level.