Check hard disk Integrity to rule out disk faults

Boot the computer up in single user terminal. On chime press Command + S and run file system checker and repair

/sbin/fsck -fy

Reboot as follows:

/sbin/mount -uw /
reboot

Repair Permissions

Open Disk Utility and choose your main hard drive from the sidebar (in most Macs there will only be one.) Now click on First Aid and Repair Permissions. This will ensure that all the files on your Mac have the correct permissions, which will help keep things ticking along.

From El Capitan onwards Disk Utility does not have this options. Instead you have to use command line version:

sudo /usr/libexec/repair_packages --verify --standard-pkgs /
sudo /usr/libexec/repair_packages --repair --standard-pkgs --volume /

Purge system and redundant files

Install CCleaner

Run as Admin as follows:

$ sudo /Applications/CCleaner.app/Contents/MacOS/CCleaner 

Install Clean My Mac 3 (paid for app)  and select Smart Clean. Optionally go through the individual options

Remove unwanted Startup items

Open System Preferences and click Users & Groups. Now click on the Login Items tab to view which programs and services are launched when you first power up (or log in) to your Mac. Highlight an item in the list that you don’t want and click on the Delete from Login Items (‘-’) button at the bottom of hte list.

Reveal CPU Hogging applications with Activity Monitor

If you want to see what apps are using up your system open the Activity Monitor in the Utilities folder. Activity Monitor shows all the processes on your Mac (some of which you can’t, or shouldn’t, close) so click on View and Windowed Processes. Now click on the CPU button and the “%CPU” column to list all programs by the amount of CPU they are using. You can also use this to see what Memory, Disk and Network different processes are using.

Delete big, unused files (also an option in Clean My Mac)

Now that you’ve paid some attention to your applications, it’s time to look at the files cluttering your drive. You can use Finder to search for huge files. To do so, open Finder and select the volume you’d like to search. Next, choose File > Find (or hit Command-F). Click on the Kind pull-down menu and select Other. When the Select a search attribute window opens, check the box for File Size, uncheck any other boxes, and click OK. Change the “equals” pull-down menu option to “is greater than” and then change KB to MB. Enter a minimum files file size such as, say, 100MB. You can then delete any files that show up on the list that you no longer need — or move them to an external drive.

Remove Custom Preferences

Open System Preferences and check in the row at the bottom. This is where custom items are added to your System Prefernces and if you’re not using them then they are taking up your CPU. Right-click on an item and choose Remove From Preference Pane.

Performance Boost

• Increase RAM to 8GB+
• Replace HDD with SSD

Useful Stuff

Enable Read/Write of NTFS Disks

diskutil info “/Volumes/MyPassport” → display Node Name = disk?s?w
hdutil eject “/Volumes/MyPassport” 
sudo mount_ntfs -o rw /dev/disk?s?w “/Volumes/MyPassport” 

MyPassport = example volume name,  \040 represents a space

Alternative method

Edit fstab and add label – LABEL=My\040Passport none ntfs rw,auto,nobrowse

sudo nano /etc/fstab

Eject then find hidden mounted NTFS volume in Finder > GO open /Volumes

MAC Terminal Command Reference

www.ss64.com

Repair WiFi – alternative solution

Turn Off Wi-Fi from the Wireless menu item

1. From the OS X Finder, hit Command+Shift+G and enter the following path:/Library/Preferences/SystemConfiguration/
2. Within this folder locate and select the following files:com.apple.airport.preferences.plist
com.apple.network.identification.plist
com.apple.wifi.message-tracer.plist
NetworkInterfaces.plist
preferences.plist
3. Move all of these files into a folder on your Desktop called ‘wifi backups’ or something similar – we’re backing these up just in case you break something.
4. Reboot the Mac
5. Turn ON WI-Fi from the wireless network menu again

If not fixed try these steps

1. Open network preferences from your WiFi icon in the menu bar. Then click advanced. Delete the network that is giving you problems.
2. Open Keychain (Utilities). Find the passwords that are stored for your particular network and delete them.
3. Repair permissions using the Disk Utility.
4. Reboot the computer.; re-enter your WiFi key log into the network.

Uninstall MacKeeper

Cancel your subscription via the integrated technical support chat before uninstalling – saves having to phone up afterwards. To uninstall quit MacKeeper  and drag the app in the Applications folder to the Trash can.

More details here from Macworld.com

http://www.macworld.com/article/2861435/software-utilities/how-to-uninstall-mackeeper-from-your-mac.html