I have been backpacking through Greece and all it's lovely islands and now I'm doing the same in Malaysia. Something I have learned is that it's not easy to pack the right things. Today we are used to pack suitcases full of clothes for only a one week holiday. Therefore it can be hard to narrow it down when you are packing your backpack. Here are some tips for what to pack and how to pack sensibly.
Wether you take a train, the bus or a boat from one place to an other, there will be some waiting and some time to spare. Therefore it's important to have some entertainment with you like: an iPod, for listening to music at the train, or a book for reading while waiting for the boat. The only thing you have to remember is that it should not take a lot of space. You don't need to bring five books, you can bring one book instead and when you have read it, you can leave it at a book café or at your hotel/motel. Afterward you can buy a new book or ask for one where you are staying. If you meet other backpackers you can ask if you can exchange books, cards or magazines. I would recommend having the book or iPod a place where it's easy to find, in case your bus is delayed, so you don't need to unpack your whole backpack to find it.
One of the things I did when packing was that I rolled all my clothes so they would take less space in the backpack, at the same time as they don't get wrinkly. I would also recommend having some sort of protection (like a zip-lock bag or a canvas bag) on the outside of your sunscreen and shampoo, in case of a leak. If you bring a canvas bag and a beach bag, you can use these to separate clothes and chargers so it's easier to find things in your backpack and have a better system. Don't pack your backpack entierly full before leaving, because this will only cause problems later on your journey.
Sunscreen, mosquito spray and makeup
It can be hard to know how much sunscreen to bring. It depends on how long you are planning to stay and where you are going, but I would recommend bringing one sunscreen with a high sun protection factor, because you don't know when you can get one again. They do sell sunscreen basically everywhere but different factors that are normal in different countries, therefore I would use a sunscreen with a high factor at the warmest part of the day, and use an other one for the rest of the day. Lush sells sunscreen in heard form, which you use when you shower, if you are going to a country like England, this is a very good choice. The same goes for mosquito spray. When it comes to makeup I would only bring the most necessary. Most backpackers does not live in luxury when traveling, so consider how important the makeup is before you pack it. You need all the space you can get when it comes to your backpack.