Cleanup junk files with tools like CCleaner and System Ninja.
Check for malwares - Roguekiller, adwcleaner, MBAM
Check for fragmentation and defrag if required (Not to be done on SSD)
Remove unnecessary programs from startup
Check that the partitions have at least 20-25% of free space
Uninstall crap that comes pre-installed with OEM Windows (If you know how to identify the crap that laptop manufacturers bundle with the OS, you can remove them manually. Else, use tools like PC Decrapifier