If you have already installed GIMP 2.8+, then you're off to a good start. Now we're going to change a couple things from the default configuration to make GIMP a little bit more useful and intuitive; or at the very least, more like the image editing programs we've become accustomed to.
This is a big one. First, you'll need to download layerfx for GIMP 2.8. Yes, for some reason it opens as a text file in your browser instead of downloading as a file. That's ok. Left click once on the text (anywhere). Select all (CTRL + A) and copy (CTRL + C).
Note: The reason I suggest using the python version (.py) is because it allows Previewing.
Now, open up terminal. Create a new python plugin in your GIMP plugins directory:
cd ~/.gimp-2.8/plug-ins sudo gedit layerfx.py
Paste the contents of the layerfx python plugin (CTRL + V). Save and close the file.
Now back in the terminal window, set the permissions on the layerfx plugin file to be executable:
chmod +x layerfx.py
Finally, open GIMP. If you had it open already, close it then reopen it.
If you installed the plugin correctly, you should be able to reach the layer effects menu at Layer -> Layer Effects.
For more info about the Layer Effects plug-in, see:
Select Layer with Left-Click
If you have ever had to chop up a layered image composition for a website or GUI, you know why this is useful. Being able to left click on a layer to select it can save you tons of time that would otherwise have been wasted searching through hundreds of layers manually.
In GIMP, go to Edit -> Preferences. Now go to Tool Options. At the bottom of this screen, you'll see a check box with the following text next to it:
Set layer or path as active
Check this box and hit "OK."
Now when you are using the Move Tool and left click somewhere in an image, the layer you just clicked will become the selected / active layer.