Make sure to acclimatize gradually before reaching Ladakh. We took the road from Sonmarg to Leh in our case instead of landing at Leh airport directly.
The altitude can hit you badly and spoil your entire trip. It would be advisable to do a course of medicine with proper guidance from a certified physician.
Please also carry cash as it is quite inconvenient via other payment methods for most parts of Ladakh.
Make sure to carry a postpaid connection (preferably Airtel or BSNL) to stay connected with family and friends. It's best not to experiment with food. We had instant noodles throughout our trip. Please carry emergency supplies of medicines, extra water, and oxygen cylinders. Last, but not least please carry warm clothes as the nights can be freezing cold.