Rule 1: Don't bother with the hair straightener. Beach hair and natural fizz make you look like your on holiday anyways. Not only is it a waste of space, it's a waste of time when you could be strolling cobblestone streets in Italy or learning to cook duck confit in France.
Rule 2: Your going to have to get used to people asking you- "Don't you own any other clothes?". Your also going to commit some fashion crimes; hiking boots in night clubs, havianas on European streets in mid winter, stained and ripped clothing in locations which require respect. As long as you stay away from socks and sandals all should be forgiven.
Rule 3: To minimise the number of fashion crimes you commit, find yourself some super versatile shoes. When Alex and I went travelling I had these great pair of brown jelly sandals. I wore them to the beach, to restaurants with white linen, on bush walks in the mountains and even to a couple of nightclubs.
Rule 4: Layer. Underwear, singlet, thermals, t-shirt, long sleeve top, cardigan, jumper, jacket, ski jacket. Do whatever it takes to keep warm with what you got.
Rule 5: If your travelling with a friend, share the load. There is no point in carrying around two pairs of nail clippers and several bottles of shampoo.
Rule 6: Take multiple forms of dosh. This means, credit cards, debit cards, travellers cheques and local currency. Also make sure to let your bank know that you are going away in case of any money glitch.
Rule 7: Pack a deck of cards. Small and light, so many uses, from curing boredom in airports, drinking games in hostels and a place for people to write down their number.
Rule 8: Take one book and trade it. With the number of interesting travellers you come across while away, chances are you'll be able to trade in for some pretty epic reads.
Rule 9: Write a journal. The hilarious things you find, months and years after you have been away. E.g "Passionfruit shakes in Cambodia are great! Minus the scary bits of meat".
"Our hostel is in a fantastic location... in the middle of the red light district".
"Then out of the blue, a lady threw a bucket of hot water at me".
Rule 10: Don't worry if you've forgotten something. You can always buy it when you arrive. As long as you've got your passport, your good to go.