One thing I want to add is always try to maintain 20-25% free space. Don't pack it full.
I have learnt the hard way that some free space is better spent as UNALLOCATED SPACE following the last partition on the SSD.
I understand that Unallocated Space is just as good as free space within the partition(s) so far as "TRIM ... all that good stuff".
I regret a default Windows 7 installation that allocated all the space available on my SSD because :-
I use Macrium Reflect partition image backup and when things go wrong it only takes a few minutes to restore the previous normality,
and after restoring I can NORMALLY continue to use SMALL Incremental and Differential backups based on the same original LARGE Full image backup.
BUT
the last time I did such a restore I first of all followed recommendations to securely erase the entire SSD to give it a clean start,
after which everything worked perfectly UNTIL I made the next small Differential Backup - and that failed and then created a new LARGE Full image backup,
which consumes more space on my archives.
The reason it failed was that when I ran the OCZ software to erase their SSD, there was also a firmware update,
and my 60 GB SSD shrunk by a couple of MB, so when Macrium restored my backup it had to fit a 2 MB smaller partition,
and when I wanted a Differential backup Macrium needed to access a FULL image that was the same size as what I had been reduced to.
It is the SSD firmware that determines the percentage of the Flash Cells that excluded from space available partitions,
and I guess the latest firmware excluded a little bit more - though OCZ deny that it was the fault of their firmware.