Guys!!
Lightroom and anything like that, any software like that are fine, but...
The OP is using an external hard drive, and since those things can be carried anywhere, moved from one computer to another computer, so the OP could if he/she wish, carry his/her external HDD to a friend's home, and hook up to a friend's computer, and access files, no different from using a USB memory thumb or a CD-R/DVD-R, so not everyone have Lightroom, and it would still make sense to still arrange the files on the external HDD in a suitable filing system suited to the OP.
To the OP: It is your HDD and your files, so you should treat it no different from your own personal hard stuff, by "hard stuff" I meant your books, your DVDs, your CDs, or whatever you collect. Maybe you have books and you are the kind of person who prefer to sort your books by author? Maybe you prefer to sort your DVDs by titles? Maybe you prefer to sort your CDs by genre such as Rock'n'Roll, Classic, Heavy Metal, etc. So when you think about creating folders to file your photos away, just think of it as no different from how you put your books, DVDs, etc., away. If nobody can tell you how you should sort your books, not even the publisher should tell you to sort by author or by titles or by ISBN, then Microsoft nor Apple can't tell you how you expect to file your photos. (Expect for computer system rules such as you can't use : or \ or similar.)
You could create folders that are major genres, such as
People
Events
Projects
Life
then you could create sub-folders depending on what you usually take photos of, for example...
People\Family
People\Friends
People\Weddings
Events\Football matches
Events\Outdoor concerts
Events\Airshows
Then if needed, a few more folders, like...
Under the People\Friends folder, are just your photos but
Under the People\Weddings folder, you could create two more folders, like folder for 'Wedding of John and Jane', folder for 'Wedding of Ben and Becky'
Or instead, you could create folders based on dates if you are willing to create indexs, such as folders...
2013
2014
2015
Under each folders are Months, like Jan, Feb, etc.,
Then in those folders are the files, and in word processor or database or simliar, you index them like
John Smith.
x:\2013\Mar
x:\2013\Jun
x:\2014\Aug
Jane Smith.
x:\2014\Feb
unless you're really good at remembering dates.
You could just treat them in the same way as you would if it was a roll of film, like when you go out and take photos, then upload form the camera to the HDD, just create a folder with some code, like A001, A002, A003, or 2013A, 2013B, 2013C, or anything like that.
I am sure many others would give any suggestions of their own, i could offer various ideas and examples, but here's the thing, you can change your computer from PC to Apple or Apple to PC, and you can change your software like changing your Lightroom for Corel PHOTO-PAINT or anything like that, or you could take your external HDD to someone else who don't have Lightroom, so really, you would still have to try to think about creating your own folders on the HDD.
Just treat the HDD and the folders just as you would in the old days of when you used to have film, and you have your ways of sorting out your negs and prints.
By the way, I took photos of the same woman modelling in different clothes, so my filing system was like group the same clothes with main numbers followed by each photos with frame numbers, for example: if she worn a white jacket, it would be 01-001, 01-002, 01-003, and so on until the last frame number, could be up to 50, 60, or so, but just in case of going over 99, hence three figures frame number, then she changed clothes, so if it is this time a black coat, it would be 02-001, 02-002, 02-003.
There are many ideas, actually it would be easier to toy around with ideas by writing it down on paper until you get a system that works for you.
