I have recently started using GTD for anything and everything I do at home and office. I now definitely see the difference between a day with adhoc and some (yes, you missed the word recently at the start of the post) planning.
I would recommend to go buy this book by David Allen, and of course read it. But just in case, you are like me who wants to get a quick summary of what to expect in a book before buying, see this excellent blog and specially this document that should take your 5 minutes to get the feel of GTD.
This is just a starter, I will post my own setup of GTD with all the apps and process that I use personally, may be something later this month.