1)In summers, days are pleasant yet cold but nights are very cold. So by no means you can ignore your best wind cheats and other woolen clothing. Make sure you wear atleast 3-4 layers of clothes the whole time
2)Due to high altitude, extreme exertion or even simple activities can kick in symptoms of Acute mountain sickness which should not be ignored in any case.
3)Basic amenities like internet, telecom services, common ration items, common food items and even water may be scarcity in that area. Make sure you have proper arrangements of those or atleast have a plan in emergency cases.
4)Know about the current weather reports of areas such as Zanskar because it changes very quickly and can become pleasant to hostile in a matter of hours.