DI and AR form an integral part of every competitive exam. Some exams have complete section on DI and AR, some exams have DI clubbed with Quant and AR could be separate. Since DI involves lots of calculations and approximations, so you need to revise tables along with percentage chart i.e. conversion of fractions to percentage and vice versa. Learning tables and percentage chart would help you in increasing your calculation speed and you will be able to approximate in a better manner. Besides that you need to revise the basics of all the types of graphs that are primarily asked in the exam i.e. tables, pie charts, line graph and bar diagram etc. Practice DI to the fullest as this is the only way to crack this section. As far as Analytical Reasoning is concerned, there is no theory for the same. You should just go through the solved examples given and get the approach of solving these types of questions. Read and grasp the concepts of some important topics like Syllogism, Logical Connectives etc as it would help in understanding the topic better. Getting exposure to as many different sets of AR as possible would make your horizon wider to deal with the AR questions. In AR, the only success mantra is PRACTICE, PRACTICE and PRACTICE.
These days questions do appear from an area that can be broadly defined as data and reasoning. It basically gives you data in some form followed by sufficient information in the form of directions. After the interpretation of the data you have to follow the given instructions logically to answer the questions. These sets have a strong application from the concepts of Venn diagram or set theory. Revising these concepts and solving some quality sets can make you perform better in the data and reasoning questions.
Mastering DI  Tricks & Traps Bar Diagrams  
Data Caselets  
Pie Chart  Angles, Values, Times  
Line graphs  
Use of weighted average in graphs  
Data Interpretations  Bar chart  
Data Interpretation  Tables 
Achievers Classroom  Data Interpretation Advanced 1

Percentage Change & Approximation Basic

Data  Lines & Bar Graphs

Pie Chart

Percentage and fractions

Data Table Test 01  
Data Table Test 02  
Data Table Test 03  
Data Table Test 04  
Data Table Test 05  
Data & Reasoning 102  
Data & Reasoning 101  
Data Basic  01  
Data Basic  02  
Data Basic  03  
Data Basic  04  
Data Basic  05  
Data Basic  06 