Use Spaces rather than Tabs
It's important that a development team use the same space/tab setting in their IDE's, else there will be many unnecessary code merges.
In the bottom of the document window >> Click Tab Size and select 4.
In the bottom of the document window >> Click Tab Size and select Soft Tabs (Spaces)
Convert existing Tabs to Spaces
Select all text in current document.
Main Menu | Text | Convert | Tabs to Spaces
RubyMine and IntelliJ
Preferences | Code Style | General >> Uncheck Use tab character
Preferences | Code Style | General >> Set Tab size and Indent to 4
There is a setting in IntelliJ that will auto-format a document upon each save.
You definitely want to have everybody using the same code formatting rules if you use this.