Trimming the fat on an SSD. Post-installation tips?

Hello.

I've been reading up on this site for tips on managing an SSD, but I'm still getting just a bit closer to the device's capacity than I want to.

I bought a 64-gig SSD with the intention of making it the drive I install the OS on. So far, so good. Followed a tweak guide and freed up some more space.

I'm at 13.1 GB free on the thing, and I just want to see what I can do about trimming the load just a little more. I just want the OS on this drive, so if there's anything being put here by default, I'd like to know how I can change that. I've been wanting to change the location of the Default User Profiles to a partition on the HDD. I've just been sending everything there manually, though, as if that's been the default location all along.

Assuming I've since added nothing to the SSD (not even games) since I've installed it, what does the system do that it more space is eaten up by default? What can I move out of the SSD's system folders onto the HDD? I've asked the question before but I don't remember which is safe to move and which isn't. I would imagine that I'd want to keep all the Windows folders on the SSD, since, y'know, that's where the OS is. But Program Files and such?



Thanks.