When taking your photos, make sure to avoid shinny surfaces. The shine from a glossy tombstone or pane of glass etc. Oh, and never try taking photos through a glass window. It's just to easy to create shapes that aren't really there. Not worth wondering if it was created from the glass or not.
Old glass is the worst.
Make sure your camera lens is clean at all times. Again, this can cause anomaly type images to appear. If the lens has a smudge it can easily show up on several pictures and can look like an anomaly, so look for that sign. Try to always keep your lens spotless. These can appear as a vortex or other ghostly images if left to dangle free from the camera.