There are a bazillion how-to tutorials on getting Ubuntu onto your computer. I'm not going to cover that. This is all about pimping your desktop to look all awesome and cool AFTER you have a fresh install. If you are stuck, there is this: a really helpful website where you can type in your question and it will give you a list of results on how to do it; here.
So, I went ahead and did a full, fresh install of the new Ubuntu 12.10 Alpha 3. After an initial crash during installation and about two hours of nail biting and not permitting anyone within at a three meter radius of my laptop, I got it to work.
It was clunky and slow and my heart was sinking. It was then that I typed in this magical sequence into the Gnome-Terminal:
sudo apt-get update && apt-get upgrade
About 15 minutes later I rebooted my netbook and nearly creamed my pants. Everything was awesome. Like, surprisingly so. So far I have found it to crash less often than 12.04, and often it is only due to me playing around with advanced settings such as compiz-config or the such.
The Ubuntu default theme, IMO, is ugly as hell. Well, maybe ugly is not the way to put it. Some people obviously like it. I just think it's not for me and I need to change that stuff ASAP to something... cooler.
The first thing I did was manually install this icon theme: AwOken
The instructions I give now can be used for any icon set you like, but I love this theme and will use it for the tutorial. The AwOken theme actually has an installer script and ppa to make things a LOT easier if you are doing this in 12.04, and there are ways I could have done it that way in 12.10 also, but this is how to do it the manually, using the super-user file manager rather than too much command line.
Word of warning! Using the file browser (nautilus) like this is very dangerous if you do not know what you are doing. If you delete anything it is gone forever. Use it with respect and follow these instructions to the fullest. There is a reason the ability of the use of the file manager like this is hidden to the average J. Random user! You have been warned!
Boom baby! You are now looking at the super file browser, now you hold CTRL and press L and you can type in the following to navigate to the required location: (replace username with, well, your user name)
This is where you want to dump the extracted theme folder, in this case AwOken.
*Please note: You don't really have to use 'sudo nautilus' to do this, but by showing you how to now, you can use the same process for other theming other things later. Close you Super Nautilus. Don't play around in there unless you need to!
Now when you install Ubuntu Tweak the AwOken icon set is selectable. Start downloading the .deb file for Ubuntu-Tweak from the link I just provided. While it's downloading, in a terminal do this:
sudo apt-get install gdebi
When the file is downloaded, select 'open/show in folder', right click and install with gdebi. This makes the new package install more like a .exe in Windows rather than being forced to use the Ubuntu Software Manager. It is quicker and easier but you can do it without gdebi if you want.
On with the THEMES!
By far, so far, the best theme I have found for the GTK3 engine is this: OMG Dark! Now, where the tutorial there says "To install themes,unpack archive to /usr/share/themes or ~/.themes folder" you know how to do it with your Super Nautilus, and do it in a hot, sticky, GUI way. Again, you can now try out these themes with Ubuntu-Tweak, like we did with the icons. I also highly recommend getting the program 'MyUnity' for even more tweaking/adjusting the look of the unity panel and bar. You can also use MyUnity to change the GTK/Icon themes without Ubuntu-Tweak if you wish.
sudo apt-get myunity
Here is a couple of screen grabs of my current desktop for you to fap over:
Oooh yeah, all nice and GUI <3