@Oldsmobile_Mike
Hey Mike, I have 3.9 and did everything as suggested and after reboot i got the Amiga dos screen so something's off with that TLSFmem, at least for me it does not work? So I booted with a workbench floppy and replaced the existing startup-sequence with a backup one and now it's back to previous/working setup.. thank G for having a backup in TEMP folder. 
You should always make a backup of your Startup-Sequence before making any changes. You can use a utility like Directory Opus or DirWork to do this, or do it through the shell. I would typically just do something like "copy S:Startup-Sequence to S:Startup-Sequence.bak", that way if things get all screwy you've got a copy right there to restore from.
Not sure why people are still having problems with TLSFmem, but I figured I'd wind up having to make a screenshot, so here's a copy of my Startup-Sequence from another thread, with notes.
Remember - it should go at the very beginning, after any lines that trigger a reboot. That means if you're running 3.9 the best place to stick it is right after the ROM updates are soft-kicked. No arguments are needed, just stick TLSFmem into your C: directory and run it as "C:TLSFmem" (without the quotes).
If you want to check what version of it you have, just drop down to a shell prompt, CD into the C: directory, and type "version tlsfmem". You should have 1.4, 1.6, or 1.9, depending on where you got it.
TLSFmem isn't a magic bullet that will make everything faster, it's just a patch to prevent memory fragmentation. I'd link to a copy of the technical details but the author's website appears to have gone down sometime in the past couple days. Here is a link to it's original announcement here on this site:
http://www.amiga.org/forums/showthread.php?t=47129Last, you should get rid of any other patches that also change how memory is managed before running TLSFmem since they might cause conflicts.
Thanks Chris Hodges for this great program!
Screenshot below: