Bear with a long post, as it is impossible to give explanation of a wonderful experience in few words.
The best time to visit Aurangabad is from August-October when the rains have subsided, and leaves greenery behind. The weather remains cloudy and is less hot and humid, making it perfect and comfortable to explore.
Reach Aurangabad from CSMT- Mumbai by Nandigram Express at night around 12. Check-in to the hotel, and have a nice sleep as a tiresome day is awaiting when you wake up the next morning. Your day 1 journey starts here.
Freshen up, get ready and if you are staying near the railway station then do have a cup of tea at the Sagar Amrutulya Tea store, just opp. of the station. Start your journey to explore the Ellora Caves at around 9 o'clock. The caves are approx 30kms from Aurangabad. Have your breakfast at the Ellora caves. There are plenty of amazing restaurants including pure veg ones as well.
Start your tour with the gateway for amazing architecture that will take you into the past. The most famous cave of the Ellora is the Cave no 16- The Kailash Temple. It's the first cave which is right at the entrance. All the caves are Monolithic (built of a single rock), carved from top to bottom and from outside to inside. The carvings and the thought put behind in the making of every single carving will mesmerize you for sure.
Suggestion: Do not forget to take a guide for the explanation. Appoint an ASI guide who will explain all the important caves. He will charge around 1600 INR for a no. of caves. But trust me it's worth it.