How to show FPS and ping in GW2

Left-clicking on the ground is the most reliable way to deselect all targets.

ESC deselects any selected targets, but if nothing is selected you will bring up your menu (can be annoying mid-combat).

There is also a key binding to target the nearest ally, which will select yourself if no other allies are around. This is useful if you are having trouble finding a patch of ground to click on. This key is not assigned by default, so look for "Nearest Ally" under Targeting in Options->Controls.

You can also select the next closest target using TAB, in case you do actually want to direct your spells towards a different enemy then the one you current have selected. Then again, a left-click on the target works more reliably if multiple targets are in view.

There is also a Guild Wars 2 printable keyboard layout to help you visualize the default key bindings.

In order to participate in guild functions such as Chat, as well as to take advantage of various guild perks, and to contribute towards guild progression, you'll need to Represent that particular guild.

You can do this by pulling up the guild menu, and clicking the "Represent" button at the bottom of the screen. Additionally, while you can join multiple guilds, you can only represent one at a time, so you won't be able to participate in guild chat from multiple guilds simultaneously.