DISCLAIMER: Make sure to @storeall before deleting your character. You are responsible for your own actions. The GM team cannot and will not recover deleted characters, and will not compensate any losses due to users' own actions.
Login to your character.
If you've ever used a cart, empty it (Alt+W).
Alt+G > Guildsmen Info > Right-click your character > Leave Guild
Escape key > Character Select
Select your character.
Click the 'Delete' button on the bottom-left.
There will be a timer in red text above your character. Wait for 10 minutes. The timer indicates when you will be able to confirm the deletion. Clicking 'Cancel' will put a stop to the deletion and the timer.
After the 10 minutes are over, the timer should turn blue. Click on the 'del' button on the bottom-left.
You will be asked "Are you sure that you want to delete your character?" If you're sure, click 'OK'.
You will be prompted to "enter the deletion password". This is usually the email that you used to register your account. If you get an error, try this:
Copy the email address directly from the page and paste it to Notepad. Make sure it's correct without any extra spaces or missing characters. Copy it from Notepad and paste it to the answer box on the ExperienceRO client then click 'OK'. If you still get an error:
Try your birthday instead (format: YYMMDD). If you're born May 27th 1993, for example, your password should be 930527. This works for some players instead of the registered email for some reason.