I had the worst experience I suppose one can experience. I hosted my sites through reseller hosting, with a very well know web hosting company. Where I used to promote their services with a smile, I can only say that if you want to get a decent web host, the rule is that you pay more for better. I got away with reseller hosting for about $25 per month and the whole caboodle went belly up when they informed me that my sites were using too much server resources. No warnings. No cheap alternative options. First off they offered a special unmanaged server hosting deal. Later on they said that it would also not be enough and they offered their managed server deal for about $175 per month. Luckily I knew someone through a membership site, who started his own hosting company, and he offered to move all +- 250 websites to his server. After that ordeal I would suggest you get to know the hosting company by asking around what people think of them. For that reason I suggest you get into contact with JayKay, the unselfish marketer, who owns the fastest autoresponder hosting servers in the world. Well, that's my opinion anyway.
Rajnish if you can tell your location may be its easier for everyone to tell the name of companies which they know in your respective location
When you buy hosting you should think where the majority of your clients are not where you are. They are the ones accessing your site, if you buy hosting in the US and your clients are in the US they will notice faster access times. But like many others have said you get what you pay for, if you want top class support you should pay the premium that some companies charge.