This post is about my experience of getting visa from various consulates when I was planning to take a stopover on my trip to US. 
I started with a plan to travel to Greece, Spain, Portugal and then couple of cities on the East Europe covering them in about 1 month. So I figured out by specified rules that I should apply to Greece or Spain consulate, as I should apply to country of entry or that of main stay.
I started with Greece, read their rules for application what they demanded:
0) Passport with 6+ months of validity from date of application.
1) confirmed return tickets
2) show of enough funds in your account, bank account statement, credit card statement
3) payslips, Income tax return receipts for last three years
4) letter from your employer showing they believe that you will come back to work with them after this vacation
5) Hotel reservations for the whole of the trip.
6) Medical insurance for the cost of the say
So you need to get your return tickets to get the visa, how the hell can u book tickets when you don't know you are going to travel. The cheapest tickets are the non-refundable ones so you can't buy them or you have to buy ones with the least cancellation charges.
I got mine from Emirates and then applied, turned out that Swine flu scare was on the go and I decided to wait/change my travel plans. So guess what I had to get my passport back so that they don't get me a visa with restricted dates.
Once I had my travel plans getting more finalized with reduced number of vacations days, I figured out I would probably get Spanish visa as that was still the main destination though Greece fell out of the plan and the new plan was Hyd-Zurich-Spain-Portugal-Budepest etc-Franfurt-SFO. So I applied to Spanish Embassy.
Their list of documents included all of above plus:
7) A statement from bank with "Stamp and signature on each page"
8) A letter from ban describing your relation with the bank
9) Show of enough means of stay (~ 120 USD) per day (apart from everything else you already showed)
10) Complete itinerary for the whole duration of the trip.
I was able to get the 6 with some effort by visiting Citibank office in Hyderabad but 7) looked like something that would take about 4 days to arrive and as I was running out of time to get the visa I asked them to see if they can process the visa with already enough proof of my "eligibility to spend time in Spain".
The VFS for Spain came back saying they would need about 21 working days to process my application. This just ruined all my changes of traveling, All I could do was to get my passport back from them and just head straight to US without any stopover. All this despite I had about 21 days of vacations to use and about 10 days buffer to get a visa.
All this exercise I had to trouble my company HR a lot get letter to the embassies, book tickets with 5000 INR cancellation fees, book hotels/hostels and additionally for step 9 I got my Eurorail pass with cancellation fees of 15%.
Luckily, some friends of mine who have applied to British Highcommision for visa told me how quick and friendly their process was. I figure out the British Consulate needed just these documents
1) Travel itinerary (no confirmed tickets, just rough plan)
2) Payslips with company stamps and sign
3) Coverring letter from HR and from self.
4) Bank Statement, proof of accomodation etc. was all optional
And the process was more staightforward, just fill a form(quite big and detailed one though), go to the local office in Hyderabad with your application and then in some time you get your Passport back by post.
More interesting they had an estimate of how much time applications take to resolve on their website, it showed all the applications would resolve in 10 working days with 70-80% getting resolved in 5 working days. This definitely is a great thing. And it turns out that my application was processed and returned in 5 working days with a visa valid for 6 months and no strict entry /exit dates. More so when the application is being process you get regular SMS notifications about the status of your application.
I simply loved the whole process and I would definitely recommend ppl trying for transits without pain to try U.K embassy.
 To give some details for reader who read this post randomly, I am an Indian Citizen, who had already traveled to Europe (Schengen visa) once, traveled 3-4 times to US already with a long duration business visa (seemingly U.K visa get processed fast if you had USA stamps already).
As another peice of advise I came to know, applying to Spanish embassy is a very bad idea, applying to Dutch, French or Germany consulate is better in that order (My experience with French consulate was also pretty positive)