To ensure that the baselines of the last lines of type sit snugly on the bottom margin, make the height of your type area a multiple of your leading. To round up or down the height of the type area to the nearest multiple of the leading value, follow these steps:
Divide the height of your text area in points by your leading increment (it helps if you use points as the unit of measurement for your vertical ruler).
Round the number up or down to the nearest whole number.
Multiply that number by your leading increment.
This number will become the size of your type area. The amount you add or subtract should be added to the top or bottom margin.
For example, if I begin with a type area of 351.331 points and a leading increment of 11 points:
Subtract 0.669 from the bottom or top margin.
While this isn't strictly necessarythe grid will still work without this stepit is pleasing to have everything align perfectly.