So here are some of my tips:
1) Research before you go
This encompasses many things. First your general research on the place you are traveling to such as accommodation, restaurants, tourist attractions, etc. But for more specifically for stock photography, look at the photos on guide books, tourism websites, stock photo sites. Find out what has been photographed before and what hasn't been photographed. What photos are popular for that travel destination. DT forums is also a great source of research.
3) Try photograph things that are generic enough to use for other things other than the place of travel. You are probably eating at better restaurants during your travels so photograph generic foods. Remember hotel rooms and other generic places.
4) Finally remember to enjoy yourself. Don't get caught up in taking too many stock photos. Remember to still take photos for your own
Anyway, feel free to add your own tips in the comments and I hope you found the tips useful and enjoyed my Japan Photo Essay.