I will also be spending 12 days in Swiss. I will be covering excursions to moutains - Jungfraujoch, Titlis, Pilatus, Grindelwald First, Glacier 3000, anyone of Matterhorn/Rothorn. Apart from this I will be sightseeing at Geneva City Tour, Lake Thun, Gruyeres, Cheese factory, Rhine falls. I have also set a day aside for sports activities.
I have the following questions.

1. As far as excursions are concerned do i need to do prior booking or should i book everything when i reach there?
2. Which one is more recommended : Matterhorn or Rothorn?
3. Do i need to book for a private Geneva city tour?
4. Is Chocolate train worth a ride?
5. What are some major sports activities that I should be doing?
6. Any more sightseeing or interesting destinations needed to be added? Or am i missing out on anything?

First of all, you should know that the country is called Switzerland, and the people are called the Swiss.

Hello peace99

"<i>1. As far as excursions are concerned do i need to do prior booking or should i book everything when i reach there?</i>"

No need to pre-book.

"<i>2. Which one is more recommended : Matterhorn or Rothorn?</i>"

Without question (between those two choices), go to the Matterhorn Glacier Paradise. The views from the summit are spectacular, especially if your day is crystal clear.

My favorite Zermatt experience is the Gornergrat. Here's a description from the Zermatt website:

"<i>The Gornergrat, at an altitude of 3,089 m above sea level, has been the top tourist destination in Switzerland for the last 111 years. The panorama is considered to be one of the most beautiful: the Monte Rosa Massif with the highest Swiss mountain (the Dufourspitze at 4,634 m above sea level), and a view over the second-largest glacier in the Alps, the Gornergletscher, as well as 29 peaks higher than 4000 metres – and everything almost so close that you could almost touch them. You can climb up to the Gornergrat on the highest open-air cogwheel railway in Europe, which departs directly from the railway station in Zermatt. From here, you can climb the mountains 365 days a year with trains every 24 minutes – over impressive bridges, through galleries and tunnels, idyllic forests and alpine meadows, passing rocky gorges and mountain lakes.</i>"

<i>"6. Any more sightseeing or interesting destinations needed to be added? Or am i missing out on anything?</i>"

I think you've listed more than enough to fill up 12 days.

Happy travels!

The Rothorn (Brienz) doesn't compare to the the Matterhorn, BUT since you will be visiting so many other mountaintops (quite expensive! and, a bit repetitive IMO), I think it is a lovely change of pace, especially when combined with a visit of the town Brienz, its open air museum, Ballenberg, and if time permits, a cruise on the pristine Lake Brienz!
As for booking mountaintop excursions, since the weather can be variable, I would wait until you are in the appropriate region, UNLESS the ticket dates are flexible.

swisshiker - I would not be able to cover Gornergrat because of time shortage. Thanks for answering the questions though!

Mokka4 - I'll google about this town, thanks