To get a "pleasing" composition, the Rule of Thirds is the first composition pillar photographers and painters will somehow use.
It is quite simple and after trying to apply it to your pictures for some time it will come to you almost without thinking.
Imagine a grid of three columns and three rows beeing put over your picture - you want to put points of interest at the intersections of the inner lines or along those lines, because that is where our eyes go first to seek information.
In the picture of St. Brendan´s Well on Valentia Island the stone cross goes along one third line and also the actual cross of the slabs is situated at an intersection of two lines.
From there your eyes are beeing led along the horizon to a small stone altar.
So don´t be tempted to center everything neatly in the middle of your picture but go for those thirds.