Referencing other sheets

If I have some formulas on Sheet 2 and want it to pull information from sheet 1 how do I do that?

To reference another sheet you type the sheet name then ! and the cell you want to reference

=Sheet!A1

or

=IF(Sheet2!A2 = "",Sheet2!A2,A2)

to make the cell equal to the value of cell A1 in Sheet 1.

Hope This Helps