Start by determing exactly what you need the machine to do. There's no point in buying a machine that won't accomplish the tasks you absolutely need it to do.
Then, find out which makes and models are available to you in India that meet your minimum requirements. Great specs and prices don't mean much for machines you can't buy or that cost so much to import that getting them is impractical.
Then, check with your friends and online to find out which manufacturers provide the best after-market tech support. I figure most entry to mid level machines are built in the same 3 - 4 Chinese factories, and once you get past eliminating models that have a lot of reported problems, the difference is the quality of the support you get when you call for help.
I can't speak for the quality of any company's operation in India. You'll have to determine that for yourself, but for example, in the U.S., I've had great luck dealing with HP, and I tell friends that the reason I recommend HP is because they're not Gateway. When I've called HP or contacted their online chat support, the first thing they want to do is help you. When I've called Gateway to help friends burdoned with their machines, the first thing they try to do is sell you something like an extended warranty.
Once you know what you can actually buy that seems to fit your needs, come on back to discuss your choices, and we'll be able to help you further.
Hope that helps.
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