As my colleague Leslie Leite has previously noted, the easiest way to for a bunch of people to work on the same documents is through the pseudo-wiki functionality of Google Docs. But if you're still sticking to the old fashioned system of emailing MS Word documents back and forth with colleagues, you'll most likely be familiar with the incredibly frustrating feeling that comes when a co-worker either edits in his contributions to an already outdated file or fails to track his changes in the master file.
A good way to prevent this from happening is to label your files clearly (and by date) beforehand (ie CloroxMarketingPlan51007), but even with that precaution in place, you're bound to have some dolt screw up the system. When that happens, you can use the "compare and merge tool" in Word itself, which works wellas long as you compare the versions in the right order. If you can't figure it outor if you've got multiple version you want to put togetherCodeJacked suggests converting your files to text files and comparing them using WinMerge, a free open source app that can save you tons of time and rage.