Let me share my placement experience with all of you just to relive those wonderful moments again .I am from Dr.Ambedkar Institute of Technology,Bangalore. It was my very first company and very first Aptitude and very first Interview .There were around 650 aspirants who participated in the placement drive out of which 250 were selected and i was one of them.
The 70 odd patterns of TCS should be more than enough to clear the aptitude (log on to m4maths.com for questions and solutions).The cut off is usually dependent on the performance and their requirements.
The selection procedure includes 4 rounds:
1.Aptitude.
2.Technical round.
3.MR and
4.HR .

My technical Interview experience:
It was around 4 in the evening n i was just coming to terms with the happiness of clearing the aptitude.We were asked to move towards the rooms where the technical rounds were going on.After waiting for some time my turn came.Here's how it went.

ME:May i come in sir?
Int:yes please.
ME:ty sir .
INT:Take ur seat.
(then he asked my resume)
INT: Hello Raghavendra plz tell me about yourself..
ME:introduced.
INT:How would you rate yourself on a scale of 10 in c???
ME:umm 7
INT:Ok..you'v mentioned your favorite subjects to be c,c++ and java would u be able to answer if i ask anything about these subjects??
ME:I try my best to answer sir.
INT:(He took out a sheet of paper with some program in it and asked me to write the output.)
ME:did
INT:hmmm good…Try writing the output of this(another program).
ME:did
INT:Ok which is your favorite core subject?
ME: DBMS and OS.
INT:Ok what is a DBMS??
ME:blah blah blah .said..felt lucky that he asked an easy 1..
INT:What is Normalization? 1NF? 2NF? 3NF? BCNF? in Detail
ME:(lucky again as i knew all those concepts very well) blah blah blah
INT:was impressed ..again took a sheet of paper and asked me to convert an infix notation to a postfix..
ME:Wrote
INT:Which is your favorite topic in data structures?
ME:Stacks and Linked Lists.
INT:Tell me 5 Uses of Stacks??
ME:Explained
INT:Differentiate C and JAVA.
ME:said
INT:Ok thats enough I'v recommended you for the next round so prepare well .
(He also gave me a hint of already selecting me by asking me to concentrate more on DBMS after being selected to TCS. That kept me going 4 the next round)

I was Directly called to HR after having to wait for a long time.I must say My HR was a real JOY RIDE.
A Lovely young lady called my name and i went inside
ME:the same old things -may i come in….can i sit ..thank u etc.
SHE:(Took my resume and immediately noticed and marked one of my hobbies that was Sketching and painting.)ahh u r an artist ??
ME: Just an amateur mam.
SHE: do u get time for such things??
ME:Ofcourse mam i paint wenever i feel bored
SHE:ie when the lecture is going on right??
ME:(Noticing her good sense of humor )May be
SHE:laughs.
SHE:Ok Raghavendra can you Tell me the two most Important things required for achieving success??
ME:well first of all v need to Dream mam.(she stared at me and smiled)and then should have the belief to achieve that.
SHE:She had an impressed expression on her face.
SHE:(some more formal questions which were in no way related to TCS or the JOB..surprisingly!!!)
ME:answered those n became really comfortable
SHE:Do U have any questions??
ME:Oh yes mam i do Where do you c TCS in 5yrs Time??
SHE:Probably beating Accenture and IBM
ME:I hope it becomes a reality mam and then asked her introduction.
SHE:I'm ***** from Goa
ME:Waw such a nice place mam
SHE: OH ok enough now u r done u may go and celebrate now
ME:(Not realizing how quickly my dream was realized)said it was indeed a pleasure talking to u mam.
SHE:Same here..

SO THAT WAS MY HR round And it was just a matter of waiting for the formal announcement which finally came at 11 in the night Of course I Became A TCSer
So My advice to you guys is not to take this for granted(Many who did finally suffered ) Prepare ypur self well and yes be yourself and never pretend to be someone u r not.they'll catch u in no time i promise DO UR BEST FORGET THE REST.
ALL THE VERY BEST.
C U IN TCS. Adias..:)