Disk Cleanup.
I delete temp files and my recycle bin.
Just seems like whatever is in there takes up over 1GB of space.
I use my computer (Win 10) for personal use and really only access the internet and do some spreadsheets using Excel.
That should be completely safe. (Assuming you didn't put something critical in the recycle bin. :-) )
There's also a good tutorial on using Disk Cleanup on Windows 10 over here:
http://www.tenforums.com/tutorials/3012-disk-cleanup-open-use-windows-10-a.html
It discusses some other options and advanced uses, which you might want to avoid for now, but maybe they could come in handy in the future.