1. Even if you think your bag is light, make it more lighter.
2. Don't take too big bags, they add weight on your shoulders.
3. Walk in your own pace. Befriend the guide at your end. They are great teachers.
4. Take hot water for drinking at higher base camps, they are safer.
5. Keep your feet clean. Take wet tissues and powder.
6. If you're a bird watcher or look out for species, pause in your trek and then watch.
7. Build your stamina before trekking, it helps the most and increases your immunity.
8. Don't ignore your illness, talk to your guides, it might be high altitude sickness. In case you're in your periods share it with your guide or camp leaders. It's nothing to be ashamed off.
9. Take jackets with hood that are water resistant. Woolen sweaters add weight and when wet, don't dry. Add poncho raincoat to your list too if your regions have chances of rain. Invest in quick dry and light clothing. When you need warmth, simply layer. Thermals can be added. No body cares what you are wearing there. 2-3 tees and pants are sufficient. Trust me!
10. I took my dslr and when the battery wasn't in use on the way, I kept it in my hands and rubbed before using it again. It went a long way.
11. Waterproof shoes are good investment.
12. Have some lone time but also have chit-chat with your team mates, it reduces your walking stress.
13. You can keep a knee cap with you. When we came steep downhill, a lot of them got problem in their right knees, including mine. Thankfully I could borrow a knee cap from another guy.
14. Keep your ID cards safe. They are to be stamped at every base camp.
15. Take a extra bag to keep your extra stuff like your travel wear at base camp.
16. Simply take a hand-towel and basic things like vaseline jelly (multi-purpose), sunscreen, little pack of facewash etc.
17. I found my fellow mates carrying novels and other fancy toiletry stuffs...Avoid-avoid-avoid.
18. Add goggles and sun caps to your lists besides woolen caps, gloves etc.
19. 2-3 friends can simply take one toilet paper roll. Many places water is shortage. Take poly bags too.
20. You can take a flat kinda plastic tiffin box, instead of plates. Take tumbler/ torch/ chappals/ pain balms and other basic things from carry list.
21. Keep cash out in your pockets. It might help you and your fellow friends too.
22. Take some chocolates and candies, You can add glucose to your water. Sip water at regular intervals. A girl got severely sick in my group, when she forgot to drink water. Got dehydrated.
23. Don't take long breaks in between trekking. Take little breaks and start walking. The 1st day is toughest, later we get accustomed.
24. The 1st trek challenges you mentally, be sound and be positive that you can do it. Enjoy the unexpected too! :)
25. Go open minded to make friends. Help others!