How best to pack for backpacking in Europe and what kind of bag is most secure?

I'm going to backpack around Europe later this year, we're going to do it mainly by trains, using an Eurorail pass, and by feet! So I'll need to pack a backpack but not sure (a)what should I pack and (b) what kind of backpack is best. Also, I'll be traveling round September/October, any idea what the weather is like then?



My main worries are that I don't want to pack too heavy a bag cuz I'll be dragging it around and am also worried about security, I've been told about thieves cutting into your bag from behind as you walk and someone told me to use a bike chain to secure my bag if I leave it at a hostel for a day. What's the best bag/backpack to carry around that's lightweight and thief-proof? And for those who've backpacked, what things did you bring? Backpackers seem to carry huge bags that look so heavy! Thanks for all the tips, guys xxHow best to pack for backpacking in Europe and what kind of bag is most secure?
the weather in europe changes alot from country to country.

expect temperatures from 5 - 20 celcius.



I suppose you are looking for something like this

http://www.pacsafe.com/www/index.php?_room=3%26amp;_action=detail%26amp;id=113

special anti-theft bags, not too big since you said you were packing light. :)



again souvenirs really depend on which country you go, but if it's for yourself, consider putting some country flag emblems on your backpack, it's nice as a conversation starter so ppl will know where you've been around the world.