1. Have the catalog and previews on your SSD. Just be certain to manually delete backups every once in awhile to keep the folder small.
2. For your Preview Cache settings:
a) set the standard preview size to a number that is equal to or greater than the horizontal resolution number for your monitor (my monitor is 1920 x 1200, so it's set to 2048)
b) set the preview quality to High
c) set Automatically discard 1:1 previews to 1 week or 30 days (not never or 1 day)
3. Under Preferences set your Camera Raw Cache setting to something like 25GB
4. You don't need much more than 8GB RAM, but 16 doesn't hurt if you are multi-tasking with something a bit more RAM hungry in the background. LR does use RAM inefficiently when doing massive amounts of meta-data updates or publishing many folders to your on-line portfolio (like Smugmug). Also, when publishing it's taking your RAW file and converting to jpeg, re-sizing and sharpening ... so it's not exactly a low resource activity.
I have 32GB RAM which is definitely overkill ... but it was cheap IMO. I've also used the XMP profile in my Asus Bios to get 1600 instead of 1333. It's easy and safe (CPU and memory was designed to do it), so why not? However, increasing RAM from 16 to 32GB and frequency from 1333 to 1600 only yields a tiny improvement over what I've provided in 1-3 above.
I also turn off "Show splash screen during startup" ... not really a speed setting, but it's annoying for me.