Any suggestions on how to keep the machine "clean" and fit; and to remove old unnecessary data stored wherever Mac stores it? Alternatively recommendations on software to do it for me?
I run a stock MacBook Pro (late 2011) 2.2Ghz Intel Core i7 with 4Gb 1333 MHz DDR3 Ram.
Initially I ran Adobe CS5.5, plus MS Office Suite and a few other insignificant apps. I also had bootcamp with Windows 7. The machine just became so slow to the point that I removed Adobe completely a year ago and am just using it for Music, iPhoto, occasional email and internet with the standard Apple software. I've removed bootcamp completely about two years and am probably using less than 20% of the machine's memory. I'm using my HP Windows laptop which I purchased four years before the Mac for most day to day "surfing" activities as it is much quicker. For work I run an Asus with SSD, which is blisteringly quick and stable. I use the full Apple suite of products in my personal life (iPhone, iPod & iPad) with numerous in the family on family share, which is the reason I'm keeping the MacBook alive. For normal work activities I use Windows and can stay on top of windows as far as housekeeping and AV is concerned, but as I only use the Apple on a part time basis I'm not au fait with general housekeeping best practices.
I have no idea how to improve the performance of this very slow MacBook and am loathe to purchase another if I'm going to struggle with similar issues down the track. I had a iMac before and that only lasted 16 months before suffering a critical out of warrantee failure .
I've purchased some software to clean it up, but that hasn't made any difference or just made it worse.
I've now upgraded it to El Capitan, which at least allows me to get iTunes going again, but the performance is still pretty slow when starting it up and trying to run applications. It is noteworthy that this machine basically struggled along before I even upgraded to Mavericks.