Hi Sachin,
On your landing page, if you are capturing the form data in the contact record, you could simply use field merges in your "thank you" email to display that data.
We have mostly stopped using confirmation or "thank you" emails for form submits. Instead we're using more confirmation landing pages(sometimes incorporating form submission data), which immediately let the user know we've received their info. We do use confirmation emails for subscriptions.
We primarily use query strings to keep track of traffic sources to landing pages. We often have several(up to 50) different sources of traffic to a landing page, so we'll tag each source with a query string so that we'll later know which sources drove the most traffic. The article Heather Bechard posted above should help.
