This should be on a letter head of the hospital, but signed by the consultant and not the head-clerk !
General letter such as “worked from ………to …………. And his work was satisfactory” is a certificate, it is not a reference. You need references.
Should the hospital be a teaching hospital, it is best. But if it is a peripheral hospital, try to get the letter from the parent hospital.
If the hospital is one of the new corporate hospitals, such as Apollo or Sundaram Medical Foundation, Leelavati or Medicare, then the first paragraph should describe the hospital itself e.g. how big, how many beds, what facilities (blood bank, all hours radiology etc.). Mention if the consultants have British and American experience.
In the second paragraph, you should mention the duration of your work, and the details of your job such as 1:3 on call, Casualty work etc. Whether you attended clinics, theaters and special clinics (asthma, urodynamics, “stress test” etc.). This paragraph should also mention the work you did in the ward including what you are good at. These are simple things such as putting IV cannulae, clerking (taking history on admission) patients, counseling and consenting them, arranging pre-op fitness and checking investigations etc. Basically, it should convince them that you can work as an SHO.
The last paragraph is the one that tells us that you have been good, sincere, punctual. “reliable” is one word they love. Do not go over the top and get the consultant to write about how their loss will be the new employer's gain etc. It is always nice if your consultant mentions that he/she will be happy to clarify any point that the new hospital may want to know.
Try to get your consultant to give an E-mail address or fax number or personal telephone number on which your new (potential) employers will be able to reliably contact them.
And lastly, your consultant should remember you and the post you did, if they ring him! So find a way to do that.
Your first job requires a testimonial, after that, your consultants write directly to the one who asks.