This a set of random tips, suggested settings and programs I've collected during the setup of Fedora on a Lenovo T420 notebook.

Installation

• Btrfs has many advantages over ext4 but it is not quite stable yet.

• Turning on compression (lzo or snappy) is a good way to increase performance. See this post if you've already installed your system.
  use the following mount options: noatime,compress=lzo.
  Warning: do not turn on compression on the /boot partition. Grub2 currently can not read compressed files. Quickfix if you've already compressed grub2 files: run chattr -R +C /boot to enable nocow (which disables compression) on the entire boot tree then btrfs fi defrag <file> to uncompress the file. (This is untested but should work. See this thread.)

•  

Post installation tasks

Install additional repositories

Install additional software

• Fedora Utils is a great tool to install additional programs and do some tweaking
  Similar programs are http://www.dnmouse.org/autoten/ and EasyLife.
  Update: Since I've dropped Fedora and switched to Ubuntu Gnome Remix, this became obsolete.
• PowerTOP is a must for all laptop users.
• Closed-source video drivers can enhance your desktop experience (video, browsing, etc.) and lower CPU usage in general.
  Frequent kernel upgrades can cause problems though. Use akmod package instead of kmod to avoid this.
  Don't forget to generate your xorg.conf after installing the drivers. E.g. for AMD run aticonfig --initial -f
  
• BleachBit is a nice cleanup tool for UNIX

Tweaks

Check my Gnome3 tweaks page for more tips and tricks regarding the GUI.

• You can tune btrfs if you skipped that part during the installation. It's not too late to enable compression.
• Check hardware acceleration in your browser!
  Firefox status page (about:support) shows that (see at the end), you can also run performance tests.
• The Flash plugin is also vulnerable to performance problems. See this forum thread. Some posts indicate this might not work with new flash versions.
  You can use HTML5 instead of Flash on many websites, like Youtube. See www.youtube.com/html5
• Tailor touchpad settings to your needs, e.g.: palm detection (it's a must IMHO), two finger scrolling, disabling tapping, etc.

Other places to check

• ModifyUbuntu has a good collection of other tips.
• Web Upd8 has excellent articles about Ubuntu Gnome and other Linux desktops.