Firstly, Download a free programme called Ccleaner, what it does it deletes all your cookies, history on your computer, So make sure any websites you want you add to favourites.
In this Picture i have deleted over 200mb, once i got over 2.5gb deleted. thats alot of memory for my laptop.
Step 1: Empty the Recycle Bin
Make sure you empty your recycle bin as it may have big files in there you dont want.