When I run the analyser, a list of suggested items is offered. How can I decide which to keep, and which to delete? Especially in registry cleaner, but also other areas.
Registry: If you don't know what it is, don't touch it. You're likely to do more harm than good most of the time.
Disk: It's all about preference. If you dont need your cookies, trash 'em. Take the time to go through the list and think about what they are and whether or not you need them. If you're not sure what something is; check the documentation or ask back here and we can advise you as to what it is.
I need help on how to research these items, so I can decide what to keep and what to dispose of.
Read the CCleaner Documentation http://www.piriform.com/docs/ccleaner/ccleaner-rules/windows-tab
Well. As they say, google is your friend. There isn't any one single source (or guidebook) that I'm aware of that discusses system cleaning. Nor are there any 1-size-fits-all tutorials.
My suggestion (as tedious as it is), is to go down the list of things CCleaner offers. Learn about each option. Read the documentation about CCleaner, search on google, ask here. Ask specific questions. Everybody is going to have a different approach as to how they go about doing this.
Some people clean their PC to make it faster, some for neatness, others for security. Sometimes they do it because it makes them feel good. Sometimes they are duped into it by advertising.
I do it because a lot of the stuff I use makes tons of temporary files that slopper-up the disk. I do it to significantly reduce the size of my backups.