Sorry I missed your deadline, but a busy week has got me well behind on my reading here. But for future reference:

When it comes to first period provisional income tax payments - In principle, what you need to estimate is the taxable earnings of the company for the year based on the information to hand, then make a payment approximating 50% of the expected tax liability for the year.

In practice, the actual value one might assign is very much situation dependant and any attempt to cover all the possible scenarios would certainly be a very long post. To give any meaningful guidance one would need some insight into your specific situation.