I’m amazed how many times I here something like “last week we had offline campaign X, could you check did we get more direct traffic than on a normal week?”. Sure we can analyze the amount of direct traffic and the search engine traffic, but why speculate when we can have more accurate data?
Firstly, on offline campaigns you should always use some kind of short url and that way people can remember those better. You should make your own short url for url that isn’t used in any other purpose. Let’s take example and we want to advertise our new power motor on Motor magazine. With the help of our IT we can choose address ourdomain.com/power that doesn’t really exist, but it is easy to remember and if people go to that address (there is no other way, because this url is only mentioned on our ad on Motor magazine) we’ll redirect the visits to the original product url ourdomain.com/motors/new/powermotors?id=motormagazine. The magic is that we’ll use 302 redirect so the analytics parameters in the url (?id=motormagazine) are coming through also and with the analytics tool we can capture the id to campaign tracking code and that way we can segment and analyze only these “offline visitors”. Same kind of logic you can use on any other offline campaigns.
EDIT: See the comments, if possible you should use 301 redirect (but make sure that those parameters are getting through too)
Sure there are many free url shortening services available, but if these campaigns doesn’t happen all the time then I would recommend to do some manual work and make the short url using your own domain, looks better. It should be also possible to build your own url shortening service with your own domain, but that would need some work… and of course, depending on the campaign, there could be some impact on other traffic sources too, even when using this kind of trick.