I have read The ABC's of Reloading by C. Rodney James and it tells me to bottom out the die against a fully raised ram, then lower ram and thread down 1/8th turn and lock, giving the stroke a cam effect. I have other sources telling me to bottom out die against a fully raised ram and lock. No reasoning is given for either method. Please help me understand which method to use and why. I understand this may be preference and not a safety issue at all but this is not an endeavor I care to stumble through. Please bear with me these first few weeks.

P.S. Anyone in the North Fort Worth area care to have a rookie watching over there shoulder next time you load some up?

Is this for a universal decapping die? If so, the depth doesn't matter, only that the decapping pin is long enough to knock out the primer.

If this is a full-length sizing die, then the whole issue of chamber length, case stretch and partial resizing comes into play. Either of the methods you described will give you a full-length resize.

What are you decapping with?

You put decapping in the caption but the question you asked really seems to be about how far down to screw your die which is not directly related to decapping.
The die only needs to be down far enough to set the shoulder back on the case so that it easily closes and extracts smoothly.
That can vary from press to press and from brand of dies even the thickness of the shellholder can make a slight difference.
If you have a headspace gauge like the Hornady it's just a matter of measuring and adjusting until
You set the shoulder back .002-.003 or so. If not just start about a 1/8 turn shy of the shellholder and keep checking how the bolt closes on the case and ease of extraction until you are happy.
I can tell you for sure if you just screw it in until it touches and then turn it down a little more until you get a cam over that eventually you will run into a larger chamber on a rifle and after about 3-5 reloads the case head will separate.

Wondering this same thing. Youtube offered little help. I followed the instructions on my RCBS die set to bottom out and then turn 1/8 to 1/4 turn and lock down. None of the once-fired brass I have would chamber in my Tikka. Sounds like there is a possibility that I am bumping things back too much?

What kind of press? If you are over sizing it should chamber easily..... it may not Fire if it is extreme but that would be unusual. With an RCBS die it would be unusual also that a 1/4 turn down after touching the shellholder if you didn't feel a heavy cam over.

RCBS die on a rock chucker press.

Is the brass fired from the Tikka you are trying to chamber it in?
If so it should easily chamber before you resize correct?
If so just adjust die until it lightly touches shellholder then size. Check to see how it chambers.
Keep adjusting down the die until it chambers as smooth as a piece of new brass.

While it's not a requirement a tool to measure case headspace helps you understand what your die is doing and gives you feedback on where you are. I love Whidden dies as he puts a gauge that attaches to your calipers in every set of dies to check to see where you are. His dies at least on my Rockchucker are a half turn from touching the shellholder. So if I had followed RCBS or Redding instruction I would have drastically oversized and had misfires.....don't ask me how I know.

All that being said I got by for 30 years of reloading without any special way to check except for running thru the gun and if it functioned all was good.

I put die depth in the caption and refered to decapping as the die in question as not to confuse it with seating. I'm talking about a FL RCBS. I need/want to get some measurement tools it looks like.

Understand and that makes sense. But they do make a die that does not size and ONLY knocks out the primer known as a Decapping die. Which is what a couple of posters thought you may have meant.
Not the same as a FL sizing die which sizes and decapps primers along with expanding the neck to to get good bullet tension.

Understood. What do you think of Larry Willis head space gauge which is actually a comparator not a head space gauge?

A comparator is all you need. You don't need headspace gauges.

Like this.

http://www.midwayusa.com/product/479704/...with-comparator

I use an old press with the lee universal set up all the time

The brass I'm resizing was not shot out of my gun. But after this run when I'm working brass that was shot out of my gun, I'll back the die off from a full length resize from now on.

You don't need all the fancy gauges, but they can help later to work your brass less. On setting up the sizing die, yo have to make sure you get a full, full length sizing. To ensure this, you raise the ram, screw the FL die down until it makes contact with the shell holder, lower the ram, and screw the die down DEEPER, about 1/2 to 1 full turn. I set up my die to make contact with the shell holder just before the ram cams over to get the most amount of leverage during sizing. The rookie mistake, or the most common reloading mistake during sizing is raising the ram all the way up, and locking your die down with the ram up. The die will make contact this way, but once you put stress on the press during sizing, the die will no longer make contact with the shell holder, and you will be sizing your brass about .005-.020" short of a FL sizing. It's just short enough to cause chambering problems.