what is the tips for cracking assistant executive engineer ?

First take overview on main topics in syllabus.
1) BUILDING MATERIALS AND CONSTRUCTION
2) STRENGTH OF MATERIALS AND THEORY OF STRUCTURES
3) RCC AND STEEL STRUCTURES
4) FLUID MECHANICS AND HYDRAULICS
5) HYDROLOGY AND WATER RESOURCES ENGINEERING
6) ENVIRONMENTAL ENGINEERING.
7) TRANSPORTATION ENGINEERING.
8) SOIL MECHANICS AND FOUNDATION ENGINEERING
9) ESTIMATION, COSTING AND CONSTRUCTION MANAGEMENT
10) SURVEYING
for preparing this vast syllabus you need to overview all topics in short time span and then solve objective questions on that topic. Start with easy topics and then move towards difficult.