1. Technical Written Round --- 30 mins and 30 questions, totally on Object Oriented Programming. Really very easy, just brush up your basic concepts. There were around 510 applicants out of which some 225 students were selected. If you are from CS or IT background, you're definitely in.
2. 2nd Written Round --- 6 mins and 8 questions on Quantitative Analysis, 6 mins and 8 questions on Verbal Ability and 6 mins and 8 questions on Diagrammatic Analysis. It was really difficult because, firstly, of the time limit, moreover, each section was further divided into 3 mins and 4 questions each. Secondly, they short listed some 40 out of the remaining 225 odd, which made it even more difficult to get through. Just concentrate and don't panic. Verbal and quants were above average, the diagrammatic part was difficult.
3. Technical Interview --- You will be asked your area of interest, i told them data structures and was further asked the comfortable zone. I said linklist, and was asked to find the middle element of a linklist of unknown length, to insert a node into a sorted linklist, etc. OOPS concepts were again tested, of which i could not answer only one question. Do go through the OOPS book completely for this interview. Was not that difficult though.
4. HR Interview --- Chill, and talk. The HR interviewers are really very cool and will just ask you general stuff as in Why Siemens? Tell me something from the past you regret? Where do you see yourself 5 years down the line? Why you? One thing, this is for every company, wiki and google everything about the company before the HR interview and also do a general mock interview with your friends, it really helps.
Once you clear the written rounds, and you are thorough with your basics in 'any' 2 subjects, you will definitely be recruited.