Framework

1. Uninstall superfluous modules
2. Remove unnecessary content
3. Install PHP code optimizer (e.g. Zend Optimizer)
4. Analyse queries and create indexes in your Drupal database if needed
5. Install and configure memcache module
6. Install advanced cache module and apply requested patches
7. In admin/settings/performance change Caching Mode to Normal
8. In admin/settings/performance change "Aggregate and compress CSS files" to Enabled
9. Install and configure QueryCache module
10. Set HTTP headers cache options to optimal values
11. Use Xdebug to find PHP code bottle necks and then optimize them

Some Generals Suggestions

Try to find a bottleneck. Do not try to optimize anything if you are not 100% certain that it causes performance problems.

Paid Services

Some of our high traffic sites must serve 5 million visits per months, 40 000 users and billions of records.

It usually takes one day to implement or guide and teach your developers to
implement most of the solutions. We charge mostly on an individual
basis, but not less than £490.

We can also provide you with some Drupal training.