When you have multiple Flex developers working together, it's often a good idea to agree upon a single syntax for .as and .mxml files. It'll enhance readability and maintainability of the code. But it'd be a nightmare trying to adhere to the agreed upon syntax manually so there's a nifty tool (Flash Builder plug-in) that you can use to do so.
Plug-In Site -
Just install this plug-in and you'll have an option called "FlexFormatting" under the Flash Builder preferences. Set the syntax rule for Actionscript and MXML and export it. Now you can give this exported file to your co-developers for one uniform syntax.
Word of Caution - We found out the hard way that if you format existing MXML code using this plug-in, the layout defined in the MXML gets messed(?) up. It's only the syntax/format that gets changed/re-arranged and property values stay absolutely the same, but layout is affected somehow. So be careful to turn on auto formatting feature if you're editing existing MXML files. Make sure the layout stays the same before committing your changes.