When you travel, there are little things that matter most. Small misses can sometimes make your journey a horrible affair. You end up coming exhausted from a trip which was originally meant to give you a break. So, here is my checklist --
Charger & Battery Packs
If you don't want worried parents/family/boyfriend/friends, do not forget to carry your mobile charger. And to be ready for the worst, carry a battery pack with an extra cable. It helps to inform your folks before you are entering a no network place. When I started traveling solo, I realized it really helps if you keep your family posted about your location - it also boosts my confidence.
Permits
To do a quick check about what permits you will need is hygiene.
Identity cards and other proofs
I wish it was different (or maybe not) but traveling means identity proofs for logins to hotels. You might need more proofs in case of special permits -- and here is where a few copies can come in handy. Last time I was in Mawphlong, I slipped into the river with my luggage - no points for guessing that some of the documents I was carrying were beyond saving.
Tickets
Going electronic and mobile has its advantages. But what if you lose your phone? Or your battery conks off the last minute. Right, am the devil here! :P
Back-ups
It can be addresses, local contacts, emergency numbers, maps -- or all of these. Make your back-ups, prepare for what might/can go wrong.
It might seem like all this prep takes out all the fun from the trip itself, but to be frank it is not so. Everything can vary according to the scale of your trip, the number of destinations you are visiting and if you are traveling solo or with friends - but at the end of the day, it is better to be safe than sorry.