If you have a nine to five job, then maybe your challenge is to not work while you travel. The hard part might be escaping the calls and emails. But when you're independent, sometimes it's difficult to harmoniously mix business with your traveling.
I offer advice on this not as a seasoned expert, but as someone who has had very productive times while traveling as well as times where I got next to nothing done. From those experiences I can share some ideas on what has and hasn't worked.
Being productive on a trip actually begins before the trip starts. At home, in a controlled environment, you can manage several things at once: optimally one big project and then a few small things like email, errands, etc. While traveling I find that the minutiae are very difficult to manage. Things like paying bills and replying to email falls by the wayside very quickly.
So for the couple days before you go one a trip, allow yourself to take time from your main focus to get ahead on the small stuff. For me, currently on a 6 week trip through China and Europe, that means queuing up blog posts, catching up on all emails, paying any bills in advance, etc. Unfortunately I did not do that, so I spent a lot of today dealing with these things at the expense of enjoying China.