This blog is not about how to identify where a field used in: reports, triggers, workflow, field update, etc. If you are reading this blog for that purpose, out-of-the-box that feature it has not available yet, so please vote this post in IdeaExchange. But, there is a workaround to find field usage using Force.com IDE, just retrieve items you want to find and find using field API name.
Ok, back to the main topic. Over time, as user request, admin create more and more fields in standard or custom objects, some of them is not so popular, may be not a mandatory in page layout. Now, we want to know, which fields are unpopular or even never used. So, it is worth to clean it. How to find it easily?
1. Export all data in CSV file
Once data exported into CSV file, use Microsoft Excel to open it, then use formula COUNTBLANK() to count how many cell with no data and COUNTA() to count how many cell with data, so the formula would be COUNTBLANK(A1:A20) / (COUNTBLANK(A1:A20)+COUNTBLANK(A1:A20)) x 100%. This will return percentage number of record with data. Then you need to copy it for all fields.
2. Field Trip
This free application create by Qandor will help you analyze the data and you can produce nice report. But unfortunately, I found not all fields are analyze, although no filter add in the SOQL. From report below, you can easily understand field like: Deleted, NRIC never used and Brand is very seldom used.
3. Salesforce Enabler
This is free plug-in for Microsoft Excel 2007 and 2010 by Taralex. Although it is not working in my Office 2007 machine, but running well in Office 2010. If you already in Salesforce arena for quite sometimes, you may be familiar with Excel-Connector http://code.google.com/p/excel-connector/, by Ron Hess. But, Salesforce Enabler give us more functions, such as: analyze objects, unreportable objects, field utilization, diff, custom reports.