Hi Vaisakh, it will take you two to three days to reach Leh from Delhi depending on how long you drive for. You can spend the first night in Manali and second in Jispa. Reserve five days for Leh and surroundings. The places to visit in and around Leh are Nubra Valley, Turtuk, Pangong Lake, Khardung-La Pass and Hemis. For your return trip you can either backtrack the same way you came or go via Srinagar. Places to visit in and around Srinagar are Dal Lake, Shalimar Bagh, Nishat Bagh, Gulmarg and Sonmarg.
If you're interested in checking out few other places on the way to leh,let me know. Otherwise the previously given responses are the one's you should follow
Since you have roughly 12 days, your itinerary can be as follows
Day 1 from Delhi to Manali
Day 2 Manali to Jispa (Better acclimatisation)
Day 3 Jispa to Leh (either can stay at Sarchu which is closer to Leh)
Day 4 Relax in Leh
Day 6 Leh to Nubra Valley
Day 7 Nubra Valley to Pangong Lake
Day 8 Pangong Lake to Leh
Day 9 Leh to Kargil
Day 10 Kargil to Srinagar
Day 11 Srinagar to Pathankot
Day 12 Pathankot to Delhi Assuming you have your own vehicle and want to do the complete circle and do not want to leave either Nubra Valley or Pangong Lake from your itinerary
Day 1: Delhi to Jammu
Total distance covered: 590 kilometers
Travel Time: 12 hours depending on your speed and breaks
Several hotels at Jammu and you will have no trouble finding accommodation in any budget range.
Day 2: Jammu – Patnitop – Srinagar Total distance covered – 300 kilometers
Travel Time – 10 hours
Visit Dal Lake and enjoy a shikara ride. If within budget, stay at a houseboat. If not, you can easily find budget hotels here.
Day 3: Srinagar – Sonamarg – Zoji La – Drass – Kargil
Total distance covered: 210 kilometers
Travel Time: 8-10 hours
Enjoy the scenic ride through beautiful Kashmir valley.
Day 4: Kargil to Leh
Total distance covered: 220 kilometers
Travel Time: 10 hours
See Lamayuru Monastery, Lunar Landscapes, Mulbekh Maitrey, Gurudwara Patthar Sahib, Magnetic Hills and Indus – Zanskar Confluence at Nimmu
Day 5: Leh
Spend a day in Leh for rest
Visit Leh Palace, Shanti Stoopa and Leh market.
Arrange Inner line permits for journey ahead.
Day 6: Leh – Khardung La – Diskit – Hunder
Total distance: 130 kilometers
Travel Time: 6 to 7 hours
Cross Khardung La on the way, once claimed as highest motorable pass in the world.
Visit Diskit Monastery, Hunder Sand dunes and see Bactrian camels.
Day 7 : Hunder – Sumur – Panamik – Sumur – Khardung La- Leh
Total distance: 200 kilometers
Travel Time: 8 hours
Visit Panamik before starting on your way back to Leh and see the hot water springs there.
Day 8: Leh – Hemis Monastery – Shey Palace – Pangong Tso
Total Distance: 240 kilometers
Travel Time: 9-10 hours
Visit Hemis Monastery on the way
Day 9: Pangong Tso Lake – Thikse Monastery – Shey Palace – Leh
Total Distance: 240 kilometers
Travel Time: 9-10 hours
Visit Thikse Monastery and Shey Palace on the way back
Day 10: Leh
Spend a day in Leh for rest before starting your return journey.
Day 11: Leh – Upshi – Chumathang – Tso Moriri
Total distance: 220 kilometers
Travel Time: 8-9 hours
Day 12 | Tso Moriri – Tso Kar – Debring – Moore Plains – Pang
Total distance: 150 kilometers
Travel Time: 8 hours
Day 13: Pang – Sarchu – Jispa / Keylong
Total distance: 160 / 190 kilometers
Travel Time: 6 – 8 hours
Day 14: Jispa / Keylong – Rohtang Pass – Manali
Total distance: 140 kilometers
Travel Time: 6 – 8 hours
Day 14 | Manali – Delhi
Total distance: 560 kilometers
Travel Time: 12 – 14 hours