I'd suggest the Fedora 20 and Gnome 3.10 as a desktop environment. I'd normally suggest to install Debian with Gnome or KDE, but Debian Jessie is only a year away, and current stable Debian is horribly out of date with the horrible Gnome 3.4 release.
As for tip for introducing Linux to people... It's important to make a clean break from Windows instead of trying to imitate Windows using for example KDE and skin it to look like Windows. That allows the people to open their minds for the fact that they're now dealing with something new and different. It might cause attitude problems at first. But those attitude problems are less problematic than the "why this doesn't work the way it works on this new version of Windows" problems when they're talking about the Linux you've installed. (I've noticed that quite many people equal OS with Windows and anything else doesn't exist in their minds even if you explain to them that GNU/Linux is a different operating system and that there are several operating systems in the world). It's also easier to tech and explain them things around the system.
It's also important not to lie about what they're using. Renaming desktop shortcut icon to Firefox into "Internet Explorer" only serves to cause confusion in people. This is especially bad since they're expecting to see "a familiar user interface" but when they see something completely different they start thinking that "I must have done something wrong" and that's something you want to avoid at any cost.
I personally use KDE as my desktop environment but, as much as it pains me, I'd never recommend KDE to a somebody who is a new Linux user. KDE just has too many things to adjust and it's unreliable desktop to use in the hands of the beginners. KDE is a powerful collection of tools no doubt about that but it has several things that work against it. KDE doesn't have a good reliable native web browser at the moment. Closest thing to that is Rekonq but it's too unstable and young project. Konqueror is also horribly out of date and it's web-browsing functionality is subpar when compared to other browsers. Opera doesn't care about their Linux port anymore but it's the closest good Qt based browser KDE has to offer. KDE also doesn't have a easy to use capable suite of office applications. If you think that Calligra is good enough, then you're lying to yourself. Skype for Linux uses Qt and is probably the best native application on the Qt side of things. Well, there's also KINO. KDE has three to four different native text editors that ship within the KDE suite, each with different levels of functionality, an tons of duplicated functionality. KDE in general has tons of dublicated functionality. Oh and we should probably talk about the KDE Wallet someday too... KDE is a very good desktop for power users but unsuitable for beginners. KDE's graphic design is also questionable because integration of components fails to meet some of the basic standards, and the Plasma is still a piece of junk. Everyday I hope that KDE project would reintroduce, bad as it was, the Kicker, back into the package. It was just way more reliable. I like KDE because it's flexible desktop but that flexibility is a very negative thing when a beginner starts to use Linux. For beginners KDE only serves as a demonstration that you can do whatever they want to do if and when they later require more functionality.
Gnome 3 as a desktop might be shit and Gnome Shell have some questionable design choises but there are several things that work for it's benefit when it's introduced to beginners or elderly. Gnome 3 has a limited amount of things to adjust in plain sight, Gnome has several native web browsers which are very capable, secure, and up to date (Epiphany (Gnome Web), Firefox and Chrome), native fully functional easy to use office suite in form of OpenOffice and LibreOffice, and let's not forget that the best image editor at the moment on Free Software camp is GIMP and it's a native GTK application. And Gnome 3.10 provides one basic application per one task to do. There are exactly one basic text editor, one basic photo library application, one basic music library application, one basic photo editor, and so on. This makes Gnome 3 easier to explain and to teach to people. Gnome 3 also comes with excellent documentation and helper applications with clean and easy to understand tutorials for everything. Gnome 3's Keychain application also better and is more transparent to user, exactly like comparable software in the Mac OS X.
Sorry about the fact that this became a rant about desktops. It wasn't my intention.