Let me start by categorising the "IT companies".

According to me, there are 4 categories.

1. Extremely Brilliant companies (Facebook, Google types).

2. Excellent ones (Adobe, Oracle India, Goldman Sachs).

3. Above average companies (which offer anything between 5lacs - 10 lacs).

4. Average companies (where 70-80% of Engineering folks are placed. Egs are TCS,Infosys,Accenture etc etc).

The only advice I can provide, pertaining to the top 3 categories, is make to Data Structures you life. Do as much coding as you can. Rest, look for other answers on Quora.

I will provide an elaborated answer for the 4th category, where majority of our fellow students are placed.

APTITUDE TEST 

First of all, you need to know that majority of companies conduct there Aptitude test online. And 100% of them are objective type.

Sections covered under this head are:-

1. Quantitative Aptitude.

2. Logical Reasoning.

3. Verbal.

QUANT 

Only 1 book - "QUANTITATIVE APTITUDE BY R.S AGGARWAL"

This book is indispensable for aptitude exams. No other book will clear you concepts as profoundly as this one. Many times, questions are asked directly from this book (with same numerical values).

Always keep in mind that not all the topics within Quant are equally important.

Lay more emphasis on topics like :-

1. Time & Work.

2. Number Systems.

3. Probability, Permutation & Combination (Little differences between these 2 topics).

4. Time & Distance.

5. Percentages & Ratios.

But, the questions asked vary from company to company, so don't take risk and try to cover as much as you can.

There are some topics which you can wholeheartedly discard :-

1. Stocks & Shares.

2. Races & Games of Skill.

3. Logarithms.

4. True Discount.

5. Banker's Discount.

P.S - This book will also help you in preparing for government exams.

LOGICAL 

As such, I didn't refer to any book for this section. But if you want, you can go for "VERBAL & NON VERBAL REASONING BY R.S AGGARWAL" 

Again, all topics are not supposed to be given equal efforts. Pay more heed to :-

1. Series Completion (Extremely important).

2. Puzzle Test (more commonly called as Seating Arrangement)

3. Blood relations.

4. Direction test.

5. Coding Decoding

Usually, from what I have seen, picture based questions are not asked. Or even if they are, they are in scarce amount. But still, I don't want you to take a risk.

Again, this book too will help you in cracking government exams.

VERBAL 

Most common questions asked in this section are :-

1. Reading Comprehension (Extremely important).

2. Para Jumbles.

3. Fill in the blanks (Based on Grammar).

4. Synonyms & Antonyms.

5. Summary of a Para (Don't worry, options will be there)

For this section, read as much as you can. Reading will improve your comprehension and also vocabulary. Reading will help you in all of the above mentioned topics.

I referred to just online material for this section.

Go to websites like:-

Make this website your bible. This single source can place you in multiple companies. It contains interview experiences, previous placement papers, section wise questions and what not. Every resource you require is there on this website.

All the Best!!!

Hello.. you need to refer to good books and in first 6 months yiu need to have clear concepts about it..