Start practicing automation testing, which allows you to run tests quickly and repeatedly without manual intervention.
The more, the merrier! Start running tests in parallel; it rapidly reduces the time required to test your code.
Start writing test data generators; it will enable you to quickly generate large volumes of test data, which can be especially useful when testing performance or scalability.
When testing web applications, start using headless browsers; it will help you test more quickly without requiring a graphical user interface.
Start including CI tools in testing strategies. It will help automate the testing process, thus, running tests automatically whenever changes are made to the codebase.
Caching test results will help you avoid running the same tests multiple times, saving time and resources.
Start using a code profiler; it will help you identify performance bottlenecks in code and draw the attention of the testing efforts to the areas that are most likely to cause problems.