The goal is to add a centered hole pattern with 8 holes:
To start I'll create a sketch on the part face to be drilled, then I'll use the Polygon tool found on the Draw panel of the Sketch tab. I'll set the number of sides to 8 and then place the polygon in an approximate location:
Next I'll constrain the polygon into place using dimensions and constraints. I'll place a horizontal or vertical constraint on one edge of the polygon to lock in the orientation:
Next I'll select all of the edges. I typically do this by creating a crossing window selection from left to right. Then I'll hold down the CTRL key and deselect the center point of the polygon since no hole is required there:
Then I'll use the Center Point tool found on the Format panel of the Sketch tab to toggle the points from a simple endpoint to center points:
Then I'll finish the sketch and click the Hole tool button. Because I have only one visible, unconsumed sketch present, Inventor automatically chooses the From Sketch placement method. And because my sketch contains 8 center points, the Hole tool automatically selects them:
And here's the result:
One reason not to use this method is that you can't take advantage of the Associative Pattern option in the assembly that allows you to place assembly components by referencing a part level feature pattern. So a little forethought in how the part will be used in the assembly will help.
With that in mind I find myself using this trick a lot. Many times I'll do this with corner hole rectangular patterns created by offsetting a plate edge:
