I hope this does not seem rude but if you are to succeed in any field of study then you will need to learn how to find things out and how to think.
Think about what you know, what you need to know and therefore what you need to find out.
Look for what you need to know.
Then think about what you have found out.
You will also need to learn how to ask questions in such a way that (a) they will get answered and (b) advance your understanding.
Asking "Can anyone assist in letting me know what items I need to specify by calculation before I start." is unlikely to get a useful answer because you have not shown that you are already trying to find out for yourself.
If you have just said that you have not started yet then why would anyone want to spare their time when you haven't give any of yours yet?
Your question is too broad to give a useful answer to.
Long before you start trying to do any calculations you would need to know what input and output voltages, load characteristics (is it a resistive, inductive or a capacitive load? Is it a constant power load?).
What range of input voltages does it have to work over and by how much can the output voltage change (line regulation)?
How much can the output voltage change with changes in the load (load regulation)?
ow much can the output voltage change with sudden changes in the load (load transient response)?
What sort of noise, spikes etc. is there on the input?
How much attenuation (rejection) of this noise do you want to achieve?
Do you need short circuit protection?
What efficiency must the regulator have (determines the choice between linear and switching or other types of regulator)?
If you can give this sort of information before you ask a question then you are more likely to (a) be able to ask a useful question and (b) get an answer that advances your understanding.
In the meanwhile: Google is your friend.
Have a look here to start with: http://en.wikipedia.org/wiki/Voltage_regulator