Tweaks after fresh OSX install

[englishpremier]

I've got my hands on a Macbook air with a fresh copy of Lion. I'm pretty new to OSX.

I'm used to doing quite a bit of tweaking after a fresh Linux install.

What are the recommended tweaks after a fresh installation of OSX?

I'm thinking along the lines of turning on prefetching (if Macs have that), enabling TRIM, adding the equivalent of noatime to the fstab, encrypting my home folder etc..

 

[englishpremier]

You may be shocked to discover your firewall is OFF by default.

Didn't know that. I figured it uses IPtables.

It's not a problem at home, but I can imagine it's a concern when on public wifi

I've noticed that accessing my samba shares is impossibly slow from the macbook