Startup disk is almost full notice! Help!

So I've been getting the "Your startup disk is almost full" warning notice pretty frequently for about a couple months now, and I just keep deleting files and applications. It's gotten to the point now that I have nothing else to do delete because I basically use most of the stuff I have on my computer, unless there is something I'm missing. I was thinking, there has to be an easier way to clean out your startup disk, I just don't know how. Can anyone help me? Thank you so much!

If you are getting short of space, either install a bigger HDD and use the current drive as an external backup, or install one or more additiopnal internal drives depending on what type of Mac you have as there is no information in your avatar or post.

For a drive to work at its peak you require about 15% free room on it.

I'd recommend you take a closer inventory of your System drive. You can do this with a program like WhatSize, which will easily tell you how the space is being allocated. I often find files that I forgot about this way.