Hello Karthik,
There are some lovely people on SCN who have gone to the great effort of creating blogs and the likes for this kind of question.
eg:
ADS Installation and Configuration in NW7.3 or higher
Setup simple ADS between an ABAP and JAVA systems
If I were the "search the community" button I'd be feeling really neglected and unloved right now.
Hope it helps.
KR,
Amerjit