Ah so you've met my wife then.

Anyway here are my thoughts.
For example - This is the fusebox on a 1979 Moto-Guzzi.
It's a simple choice of fuse as ALL fuses are switched.
If not then buy a CHEAP multimeter (eBay has loads in the USD20 range) and check fuse by fuse until you find a fuse that is only live with the ignition on.
imo you should not even go near electrics without one.
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It's not THAT EASY to see but basically there are some FASTON tyre blades that will take a standard 1/4" faston female terminal.
If there are none free (and in this case there are none) then there are solutions - don't panic.
There are piggy back faston adapters and terminals.
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Which type you choose may depend on availability and space.
You can always simply tap into the wire too.
Personally I don't like this idea but sometimes needs must.
I particularly HATE this type of tap - I've 100's that came with all sorts of accessories. All go into the "I hope I'll never need this" parts bin.
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Better imo are the taps from posi-lock
http://www.posi-lock.com/posiplug.html
Also imo if you're planning on mounting a number of accessories it's FAR BETTER to add a specific accessories fuse box.
I make up my own accessories boxes but the PC8 from EasternBeaver are highly rated and come complete with all fittings (including the posi-tap)
http://www.easternbeaver.com/Main/Wiring_Kits/Fuseboxes/PC-8/pc-8.html
I have used a fair few hardwire 12V->USB adapers - here's one with a mini-USB (and 90º adapter) that was rewired with ring terminals to fit my fuseboxes.
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But we'd have to wait for RockThinking to prepare one due to the non standard plug - My eyes are not up to soldering micro-USB connectors.
If this all seems beyond you. Find an auto electrician or a friend who REALLY knows - invite him/her to lunch or for a beer.
PS - Land-Rover photos later this week.