If you have Live View on your camera, that can be used to great advantage when trying to get perfect focus. Specially if you use a tripod. Zoom in on your screen to the part you want to be in focus, and use manual focus to get that part of the picture sharp. Then just shoot! It can be easier to see on your screen than in the viewfinder. You can also take test pictures when using a tripod, and adjust your focus if it is off. The test pictures do not have to be of greatest quality - you just want it to take as little time as possible, and then adjust to your perfect settings after you get the composition and focus where you want it.