Q: how do I clean up my start up disk

No. You are that program.

Freeing Up Space on The Hard Drive

  1. See Lion/Mountain Lion/Mavericks' Storage Display.

  2. You can remove data from your Home folder except for the /Home/Library/ folder.

  3. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.

  4. Get an external hard drive on which to store some of your files after which you can

      erase the data from your internal drive to free up space.

  5. Also see Freeing space on your Mac OS X startup disk.

  6. See Where did my Disk Space go?.

  7. See The Storage Display.

You must Empty the Trash in order to recover the space they occupied on the hard drive.

You should consider replacing the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.

Try using OmniDiskSweeper 1.8 or GrandPerspective to search your drive for large files and where they are located.