Logical reasoning is a process of passing from the known to the unknown. It is the process of deriving a logical inference from a hypothesis through reasoning. Put it differently, in logical reasoning a logical inference is deducted from statements. This type of tests helps us learn the process of elimination or deductive thinking. Most problems give various conditions and you must use an "if"-"then" strategy. Before starting to solve a problem, it’s important that you read the whole problem, and choose the best hint. It is the toughest part of any competitive examination. When attempting logical problems with reasoning making a chart or drawing a picture is advisable. 

Type of reasoning involves mainly three attributes: What? When and How?

‘Three kinds of logical reasoning can be distinguished: deduction, induction and abduction. Given a precondition, a conclusion, and a rule that the precondition implies the conclusion, they can be explained in the following way:
Deduction means determining the conclusion. It is using the rule and its precondition to make a conclusion. Example: - When it rains, the grass gets wet. It rains. Thus, the grass is wet.

Induction means determining the rule. It is learning the rule after numerous examples of the conclusion following the precondition. Example: - The grass has been wet every time it has rained. Thus, when it rains, the grass gets wet." 

Abduction means determining the precondition. It is using the conclusion and the rule to support that the precondition could explain the conclusion. Example: - When it rains, the grass gets wet. The grass is wet, it must have rained.’ (Taken from wikipedia)

A classical example:
Man is mortal
He is a man

Therefore, he is mortal (logical deduction)

Logical Reasoning Questions:

Before attempting problems on logical reasoning, one is expected to have a concern on the basics of logic.

A proposition is a statement of certain relation between terms. A term means the subject or predicate of a proposition. The subject of a proposition is that about which something is stated (Man in the above example) and predicate is that whatever is stated about the subject.(mortal is the predicate) The sign of relation between subject and predicate is called copula (is in the above example).

Proposition may be either universal or particular. If the subject denotes the entire class or group or pool, it is Universal. (Eg: All students of the college, nobody is superior).

 If only a part of the subject, class or group is considered, it is particular. (Eg: Some of the students, somebody has told)

Both these proposition can be further categorized into affirmative and negative. It can be understood from the following examples.

Universal affirmative: 1. All parents are members of the PTA.
  2. All persons are committed to the society.
Universal negative: 1. No one is beyond the regulations
  2. No stones are living things.
Particular affirmative: 1. Some officials are dedicated.
  2. Some students are studious.
Particular negative: 1. Some of the winners are not students.
  2. Some singers are not good.

Distribution of terms:

A term may have either direct/dictionary meaning, i.e., denotation or indirect /implied meaning i.e., connotation. If a term is fully denoted, it is a distributed term. Full denotation means total involvement and not partial. In case of partial involvement , it is undistributed.
In the case Man is mortal, man denotes all the human beings. (Distributed)
In the case ‘No criminal is a man’. Here the meaning of man is connotative.

These concepts can be better understood with the help of graphs and charts as mentioned earlier.
Let us consider the first example:

All parents are members of the PTA.

P- PTA
S- Parents

No stones are living things.

Some officials are dedicated.

Some of the winners are not students.

Inference

It is the process of arriving at a conclusion from more than one proposition. It can be deductive (moving from general to particular) or inductive (conclusion is wider in extent than the premises). Commonly deductive logical inference ability is tested in competitive examinations. Deductive inference is further classified in to immediate inference and mediate inference (Syllogism)

Immediate Inference

In immediate inference the conclusion is derived from a single premise. 
Eg: Statement: Some politicians are corrupted
Conclusion: Some of them are not corrupted.

Two types of questions can be set in immediate inference.

1. A statement is given and then it is asked whether the inference can be derived or not
2. A false statement is given and it is asked whether the inference are correct or not.
The results obtainable by immediate inference are termed conversion, obversion, contraposition and inversion.

Conversion: In this kind we infer from a given proposition, another proposition, by inter changing the subject and predicate.
Eg: No man is cat
  No cat is man

Obversion: When proposition is changed from negative to affirmative or from affirmative to negative without undergoing any change in meaning it is obversion. 
Eg. Some dogs are friendly.
Some of the dogs are not unfriendly
No man is perfect
All men are non perfect

Contraposition: A double change is take place in this case. First the changes is to obverse and then to converse.
All men are mortal.
No non-mortal is many. Therefore no man is non-mortal.

Inversion: In partial inversion the subject is contradictory of the original and the predicate same as original. The inverse of All Teachers are scholars is some non teachers are non scholars in this case. But in the case of the inverse some non scholars are non teachers. It is full inversion.

Mediate Inference (Syllogism)

Here two premises are given. From this the inference has to be drawn.

Eg: Tata is richer than Birla
Ambani is richer than Tata
Conclusion: Ambani is richer than Birla