There are a number of ways to align fields. If you select multiple fields, you can right click on one of them and select: Align, Distribute or Center
and you'll see all of the options available.
You can also turn on the rulers by pressing Ctrl + R, and can then drag guides from the horizontal or vertical ruler. When you drag a field close enough to one of the guides, the border will gently snap to it. The border that's closest to the mouse cursor is the one that will snap to the guide. Right-click a ruler to select the available guide options.
New to Acrobat 11 are various keyboard accelerators in form editing mode that you can enable to make aligning fields much easier. See the following previous thread for more info: Acrobat XI switch between form design & form view
Note that there is a method to paste copied fields in place and an accelerator for quickly toggling between form editing mode and regular mode (A key). Once you get used to all of these, working with fields becomes a lot faster and accurate.
Also, note the you can copy fields by selecting the ones you want to copy and Ctrl+drag. If you Shift+drag selected fields, they will be constrained in either the horizontal or vertical direction. Ctrl+Shift+drag to copy and move vertically or horizontally.