When you hear about people using a high poly -> low poly workflow for their models, "low poly" is usually referring to, say, the type of model you would see in a video game: Realistic models with not too many polygons, using normal maps baked from a high poly model to keep some of the details. If you're making a stylistically low poly object, here are some tips: Take advantage of the Decimate modifier; you can sculpt something for example and decimate it to a low-poly object. It depends though, for structural and man-made objects, your low-poly should really just use primitives (cylinders, cubes, etc). For some details such as cracks in rocks, you can use the knife tool to cut out triangle-shaped wedges and delete the faces.
There are really a couple different styles I've seen under the general "low poly" category, but in general, I find that for organic objects like an animal or terrain, use tris/decimate to tris. For things like the lighthouse in your linked album, use a normal quad workflow. Lastly, remember that when adding primitives, a menu will pop up (or press F6) which allows you to lower the number of segments on a cylinder for example.
The main thing which determines whether low poly art looks good or not is just proportions. You don't have to focus on texturing, UV's or complex materials, so the basic shapes and outlines of objects are all that there is to focus on. This can just require alot of tweaking. There are tons of tutorials online; I would recommend Grant Abbitt's to start.