How do I center an object?

I thought this worth some additional information, as I have a feeling there are some aspects to positioning objects we don't all think of.

This document is 1000 pixels square.  So long as Snap is enabled, you can drag out guides from the rulers, and they will snap to the centers (horizontal and vertical

If we zoom in far enough to see the pixel grid, we see the guides fall exactly on the intersection of four pixels.  This will only happen if the document has an even number of pixels, and the guides are NOT locked pixels

As demonstrated when the document has an odd pixel dimension.  Guides can fall anywhere.

If we drag the grid zero to the guide intersection, then the 0,0 point will conveniently 'snap' to that position.  This is handy as it gives us an 'absolute' reference point.

So when we start the Free Transform process, our object's center point is shown in the X & Y fields in the Options bar

Which we can edit and set to any position we have the pixel dimension for.  Where I find this most useful is with Free Transform Snap & Repeat when you have an angular component in the Transform.  Like when copying the number type layers around a clock face.  Even the tiniest error in the center handle reference to the clock face center, will build up with each step, and can leave you with a very visible offset by the last step.  But it is useful in any situation where you need (or just driven to by the OCD all content creators are prone to ) accurate positioning of several object layers.  I use it a lot, so obviously have to put my hand up to being OCD.

Something to remember when moving vector objects.