Choosing a distribution

Maybe I should first write about choosing a distribution, and then about choosing a DE/WM, but it's all here, so no problem.
Choosing a right distribution is a bit harder. Be aware of the fact, that in the end, they all can look the same (depending on which DE/WM you use), but they won't behave the same (read about differences between distributions). If you're not used to any package manager, then it is actually all the same for you whether you'll have a DEB or RPM distro (but once you're used to some of them, it's not that easy to switch). If you're new to GNU/Linux world, I suggest to use binary-based distribution. That way the system will solve package dependencies during the install process for you and installation of everything will be easier. I also suggest you to use distro with good repositories. That way you'll have most (or all) things you need in the distribution repositories and that will also make your life easier. Community (forums, wikis, blogs, portals) about your distribution is also very important. If you come encounter some problem, it will be much easier to find a solution to solve it. Hardware compatibility is also very important. If you have a distribution which has drivers for all your computer's components, you won't have to search for them on the internet and install (usually compile) them by yourself. Some distros have better security updates than the others. Some are more stable than the others. That usually means that you have to choose whether you want to have more stable system with older package or (almost) latest packages with less stable system. Anyway, by choosing this or that you probably won't make that big mistake. Especially, if you choose some of these distributions:

Debian GNU/Linux - One of the oldest and the most derivated distribution. It is stable, secure, binary-based distribution with good repositories, community, hardware compatibility and architecture support. Read more about Debian and choosing which one to install in next post. Always a good choice!

Arch Linux - RPM based distribution with good repositories, community and hardware compatibility. It is a bit harder for installation and configuration, so maybe not the best choice for a newbie.

LMDE - Linux Mint Debian Edition. Very popular Debian derivative. It has it's own DEs, MATE nad Cinnamon. Maybe the easiest way to start with Linux.

OpenSUSE - Another one of the most popular (not without a reason) distribution. It has RPM package manager and comes with KDE as a default DE.

Fedora - A RedHat (RPM) distribution, comes with GNOME3 and tends to be bleeding edge.

Slackware - The oldest still existing distribution. Stable and good, has independent package manager, but it is only for those who want to get into the principles of working of the Linux. Definitively not for someone, who wants to have an easy life with his/her OS.

CrunchBang - Debian forge with Openbox.

ArchBang - Arch forge with Openbox.

There are many many other very good distros, but I haven't been experimenting much with distributions so I can't tell you much about it. Check the DistroWatch site and good luck in finding your distro!