Adopt different test methodologies (test styles)
Always consider applying different test styles to your area. Each style is suited for finding specific class of issues and applying different styles gives the maximum ROI for your test effort.
Some of the approaches that have been highly effective in the past are:
1) Creation of tools to dynamically generate test cases.
2) Fuzz tools that morph the input data.

A good list of different test styles is mentioned in:

Ensuring Testability
Design for testability is an important point to be considered that greatly affects the quality of our tests. For all new features coming online test owner should have a testability discussion with the developer before feature implementation. The important point that needs to be considered here is - Can we get to all the functionality we want to test in an easy and efficient manner?

Reviewing test strategy
Feature test plan should describe the ‘test strategy’ that will be adopted and should be reviewed as part of test plan review. Primary purpose of reviewing is to share ideas and foster discussions.

Sharing ideas and information
Strive to share the following as much as possible across teams
• test strategy ideas
• test framework/tools
• Information (e.g. new feature addition) in one area that could also affect other areas.