Before I start ranting my points of view and my reasons on why people vote, let's just think up some general facts about India's elections.
1.2 billion People!
762 million voters!
~450 million people who actually cast their vote.
Now back to - Why do people vote?
Obviously the answer is for a better nation. And sometimes (actually most of the times in a nation like ours) for our own selfish reasons.
Voting essentially goes down to what Mr.A or Mr.B or anyone else is going to do that will benefit YOU!! This might sound pretty selfish and also foolish to some of you, but I wouldn't vote for Mr. X if s/he said that they’d build dams and provide electricity to some random village in a state I do not live in! I mean I wouldn't even know if they have even built them! I would rather vote for someone who promises stuff where I live, where I stay, where I might benefit and where it might help me live better!
So yea if you're voting for someone who isn't going to help you in any way, you obviously wouldn't vote - I mean, think of it, there's no logical reason for you to be such a selfless being unless you already are a huge billionaire philanthropist or are an ascetic. 
Another very important point - You don't get to vote for the leaders of the party in India, you get to vote for the local MP of that party in your locality. So what primarily matters to you is your own locality! The party president or the Prime Ministerial Candidate isn't going to do wonders in your neighborhood but your local MP might! So choose based on your local MPs and not based on the person in New Delhi!
Also based on my conversations with friends, foes and strangers, I have understood that elections and party allegiance divides people a lot in our country. And the reasons for these divisions among the people are the issues over which people cast their votes. First, it used to caste based politics and now it is issue based politics. Do you want to vote for a person who aims to curb corruption? Or do you want to vote for someone who is going to develop the country? Or do you vote for someone who comes from the oldest and the strongest political party of the country?
The issues in the upcoming elections are pretty tricky. Corruption versus Development; New versus Old; Efficiency versus Experience… and the list goes on. And then there’s the secularist point of view and also the point of view of the common man. So which issue is your priority? What is the central concern of yours that you seek resolve while deciding on whom to vote?

I don't mean to influence your views in any way. I myself am pretty confused about whom to vote for - I support a political party and also like the party's manifesto at the center but I'm not so sure about their local MP in my constituency; so I'm stuck between a rock and a hard place.
Anyway, these are my own personal points of view. They are not meant to intentionally or otherwise coerce someone into voting for one political party or the other. I maintain my opinions to myself and these points mentioned here are not meant to be taken as a complete list or an analysis and should not be used to drive you to vote or not vote for someone.
P.S - Your vote counts! It's your right, it's your responsibility and it's your future! GO VOTE! And if you don't (or didn't) vote then don't complain!! I, personally, am very tensed and nervous about voting! I value its power and I know the responsibility I'll have to carry in my heart when my vote goes to someone who ends up being a wrong choice!
P.P.S. – For all the people who say things won’t change even if you vote – well, I can’t guarantee that things will change with your vote. But I can guarantee that they won’t change if you don’t vote! BTW this time there’s the NOTA (none of the above) option, so you can go vote for nobody – rather than not voting at all!!