Simple guide to Sharing & Permissions - does it exist?

I have an external drive, and I want to be the only user account who can read/write/view the folders.

I have set up one folder with <My account name> with privilege "Read & Write" and also <Everyone? with privilege "No access".

With a second folder I have set up the same privileges.

HOWEVER - all users can access the first folder, and NOBODY (not even me!) can access the second one - the second one has a 'No entry' sign on the icon.

Neither is giving me what I want - and they are giving me 2 different results!

To me, the above permissions should only let me (Alasdair) open the folders and read/write the contents.

I'm not asking for a solution here (unless you have one :) but are there any resources which will explain this to me - I've searched the Apple Support site and wider internet to no avail. I don't want to get into command line stuff.

Thanks in advance!