Buses run directly to Leh from either Manali or Srinagar. Enroute to Leh one can stop in a number of places , most will get off in Keylong, the administrative center for Lahaul. Overlooking Keylong is the Kardang monastery. This is the choice that most travellers will want to take due to the tense security situation in Kashmir, however the road is only open from June to mid October due to snow fall. There are shared taxis from Manali which start early in the morning and reach Leh early next morning.Tourist buses from HPTDC and the local HRTC buses, stop overnight in Keylong. There are also minibuses and shared cabs that make a overnight stop in Sarchu - this comes with a high incidence of altitude sickness, since Sarchu also dubbed "The Vomit Hilton" lies more than seven hundred metres higher than Leh, at 4253m. Coming from Srinagar there are a few interesting places to stop en route : Kargil at 2693m where the buses stop, the best choice for altitude acclimatization, Lamayuru and Alchi that also offer accommodation. The opening and final closing of both roads, but no major events in between, are announced on the the official Leh website. Srinagar-Leh news updates are found here, Manali-Leh here
Daily flights to Leh are run by Air India and Jet Airways from Delhi, Srinagar, Jammu and elsewhere. These are, however, subject to inclement weather and may be cancelled at any time, keep your schedule flexible. Altitude sickness is also a worry given the altitude.
You can ride into Leh between June and mid-October when the roads are open on a motorcycle too.
Bikers usually follow either of the 2 routes
1. Delhi -> Jammu -> Patni Top -> Srinagar -> Kargil -> Leh
2. Delhi -> Chandigarh -> Manali -> Sarchu -> Pang -> Leh