Well first of all to save more space, make sure you uninstall and delete any applications, programs or files you don't need. Just pick a day where you browser through all your downloads and just get rid of anything you don't need.
Another way to save a bit of space is to .rar or .zip large amounts of files you won't need for now like photo albums or a bunch of documents that you need to keep but won't use for a long time.. just compress it into a smaller file.
Use a CC-cleaner which is a free program you can get from google. It looks for best ways to optimize your space and files.
If you have a PC, you may consider buying and adding extra GB's of RAM to speed things up a bit.
And of course going into your taskmanager to manually set the priority of your processes can speed up one process while slowing others so you kind of sacrifice "attention" from other programs to speed up 1 single program.