Q: "Other" storage

I have a late 2008 MacBook Pro 15" running OS S version 10.8.5.  I run a lot of Movavi and Aimersoft video programming devices on top of this OS.  Often, my "other" storage is high, e.g. 65 GB.  A times Keynote programs impact heavily, but when I move their output from HD to Quick Movie and from there to mp4's, & burn the mp4s to DVD 5s or DVD 9s, I still have lots of stuff in "Other" storage.  The Movavi and Aimersoft can sometimes eat up storage, but after I burn end product (the mp4 sile or files) to disk-5 or -9 and delete all precursor files (for both keynote, QuickMovie and Movavi), etc., there may be only a 3GB to 6GB  drop in "other" storage.  Have few music, TV, and music programs in storage on my MacBook.  How can I improve performance by decreasing %% of "Other" GB?  My total storage possble = 250 GB.  The MacBook Pro executes reasonably well at 110GB free.  I'm typically bogged down at 88GB free.  My Movie file for stuff downloaded from YouTube I limit to 8 to 9 GB.  For memory I have 4 GB instead of 2 GB.