this is easily the best way, no point using rulers... for an exact centrepoint with text tho you'd better convert to outlines so the slightly larger bounding box doesn't interferein the layers panel, select both the text you want aligned, and the background image layers by holding ctrl and clicking each layer. once both are selected, select the move tool (v) and in the tool options bar, at the top of the screen, will be some alignment buttons, have a play, and you will soon work out which ones will give you the desired positioning.