For both pictures, I used the quick selection tool like it said on the tutorial to select the subject matter. I didn’t really need to use the refined edges step for difficult areas because I didn’t have any hair or anything. But I selected the subject matter, then I applied a layer mask and “erased” the background by filling it in with black. Then I went back to refine the edges where the quick selection tool failed or where the edges just looked grainy using a white brush. For the bulldozer, to get those really crisp edges, I used the polygonal lasso tool on those straight edges and filled it in with black on the layer mask.
Being new to photoshop, this lesson, albeit essential to learn, was frustrating to do. I spent a lot of time on those edges trying to get them right. But the tutorial was really helpful and the longer I spent on it the easier it got. Also, it’s nice to have a wife who is a graphic design major to check your work.