UPDATE: Doing a disk cleanup

[usonian]

3. Highly recommend backup(s).

I recommend a full backup of the internal disk now and then. Disks are cheap! An external disk the size of your laptop disk (unknown) is like under $100. Cheap insurance.

For mac users:
I use a program (SuperDuper!) on macs to back up the entire internal disk to another disk the same capacity. The free version does this. The virtue of this is that if the internal disk crashes, not only is the external disk full of its contents, but is also bootable. (read the instructions with the program).

For others:
Ask someone you trust. A web search will turn up products that pay for search placement on Google and others.

Otherwise, just copy your important files and folders to an external disk as you see fit.
I personally keep all my important stuff on external disks but I am not using a laptop.