Not easy to set for up-close, still-shots!

I have had this for 2 to 3 years now, and have taken a lot of high-quality photos, mainly outdoors. Once I started needing to take up-close, indoor photos, I started having difficulty
in keeping them in focus. I have read and read through the operating instruction manual, but it's still not that clear how to best set-up for this type of photography-plus, sometimes if they look clear and in focus on your camera, once you load them to your computer, they're really terrible, and completely unfocused. My lens is now starting to go bad and not opening all the way, but it has been dropped and I travel a lot with it, so it will take some abuse, that's for sure.