Hey Rajesh,
First you learn the C langauge and configuration of AVR atmega8 controller.After that you start make some task of controller like led blinking, LCD display, sensor interfacing etc.,.
When you able to make your application start to develop application but follow some point which i mentioned bellow:
– Devide your application in sub task ( modullar approach ). For example,LDR interfacing , RTC interfacing, IR interfacing etc.,
– Make coding and testing one by one sub task.
– Merge the subtask one by one.
– Testing and debugg the code