In addition to using a version control system like Git or TFS, where a copy of working code is committed both locally and on the server, it also helps if teams have something like a 15 minute daily stand-up meeting, so everyone is on the same page about what the other is working on. For example, if John casually mentions that he's planning to refresh the development copy of the Product database from production over the weekend, James has an opportunity to point out that he and others currently have some stored procedures that are work in progress there.