1. Edit /etc/sysctl.conf and at the bottom of the file add on 2 new lines: vm.swappiness=15 and vm.vfs_cache_pressure=50. You can play with these values until you get a good feeling of responsiveness from your system.
2. Install flashplugin-installer: sudo apt-get install flashplugin-installer
3. Edit /etc/samba/smb.conf and change the workgroup name so that all of your computers belong to the same workgroup.
4. Install the printer and scanner.
5. Install wine.
6. Change the theme to suit your needs or expectations (for example, to make Xubuntu look like Windows 7 check this out. May be old, but it's a start).
7. Customize the panel and whiskermenu.
8. Edit custom actions in Thunar: mount/unmount iso image, share/unshare folder via Samba, compute md5sum checksum and other