From Forbes:

2. Implement A Decision-Making Process Around New Investments

This may sound obvious, but every time we spend cash—even if it’s within the budget—it’s a lost opportunity to save cash. Simply pausing to consider this trade-off can lead to better outcomes. This can effectively be enforced via a light, but formal, decision-making process around new investments. Follow the framework for new spending decisions and the results after six months will impress. – Erica SchoderR Street Institute