HI there
not sure of which LC you have?
Meantime you might have a read of this article to get your head around some basic mechanical terminology:
http://www.lcool.org/technical/diffs/diffs.html
On a loose surface the power will go to the wheel with the least grip so you could think of it this simplistic way:
Your 4wd is really 1 wheel drive until you start to lock the differentials
centre lock and you have a 2wd - power to front and rear.
lock the rear and you have 3wd
lock the front and you have 4wd
For me centre diff lock on anything loose - gravel, track, mud snow ice
rear locker if you need more traction (set it all in place in advance ie before you will need it - read the conditions ahead). only use lockers when you are going slowly and preferably straight as possible - the more locks you apply on the transmission the more the truck wil want to go straight on. Read up on transmission wind up.
front locker if you have one - to get you back out of where you should never have gone in the first place ;-) or need to keep going to get back out the other side.
Using lockers puts incredible load on your transmission components so would suggest you get a good understanding of what and when, and be as gentle as you can/ conditions allow. With careful thought you can get through most anything, but understanding how things work, what they are for and when should prevent you from sitting there wishing you could rewind the clock a few minutes...
Also read up on dropping tyre pressure to enhance grip (you'll need a way to get the buggers back up again afterwards).
Also make sure your choice of rubber is suitable for the task at hand.
Working out your correct route, coupled with low tyre pressures, and working your diffs etc will allow the truck to do things that will probably take your breath away, again and again.
Welcome by the way!!