Initial timing vs. total timing

Can someone explain initial vs. total timing?  Also, how to adjust them.  And how to figure out what they are if you have no idea.  

Big Welcome aboard, I'm a new guy here too.
My answer can only be as detailed as your question, next time some specifics about your truck would be helpful. You asked a simple question, the answer will not be quite as simple. Not knowing anything about your truck or it's engine I would like to give you a few very general guidelines, which should apply to almost any American V-8 or 6 cylinder built between let's say 1955 and 1975.
Before you set the timing you should know it can solve a few problems and cause many if it is not set properly. Setting the timing is also a basic part of a good tune up. Unless you have a specific problem you are trying to address you will be better off to leave well enough alone.
Before you can do anything you will need a timing light. You will also need to be able to identify the #1 cylinder on the engine. Ford V-8's are on the right side and GM is on the left (while seated behind the steering wheel and facing forward). A 6 cylinder uses the front cylider.
The next step is to find the timing pointer on the front of the engine, usually held in place with the same bolts holding the timing chain cover, it can be on either side of the engine and usually the older the engine, the easier it is to find! The actual "timing marks" are found on the crankshaft pulley/balancer (these terms wil be used to mean the same thing from here on). The timing marks are actually just small marks or lines going across the pulley. You may have to do some serious cleaning to find the marks. The pulley on the front of the engine is usually covered in grease or rust. You will probably need to de-grease or remove the rust if the timing has not been checked in a long time. I usually use fine sand paper to clean the rust off. When the pulley is clean and you have found the timing marks, it helps to make sure you will be able to see them with the timing light. Way back when, we used a yellow tire crayon, today a permannent marker of some kind will do the trick, probably just as well. I usually mark the O mark on the pulley. This indicates what is referred to as Top Dead Center or TDC and may be marked on the pulley instead of a O.  
Intial timing is the spark timing the engine will have while cranking and generally at idle when the engine is warmed up and idling at it's intended speed. The intial timing is also checked and adjusted with any vacuum hose to the distributor disconnected and plugged, (until about 1975 when things got really crazy). This is a simple but important step.
Initial timing is adjusted or "set" by moving the distributor relative to where it sits in the engine block. It actually is changing the time the spark will occur in the cylinder relative to the position of the piston.
The ditributor can only be moved after the hold down bolt for the distributor clamp is loosened. You will find this at the base of the distributor. It usually has a fork shape with one bolt going into the engine block holding it down. Or it may be held in place by a bolt that goes through a slot in a "tab" coming off of the base of the distributor. Depending on the engine a specially shaped tool can be very helpful/required to reach this bolt,especially on the GM V-8. Once the distributor is loose in the block it can be rotated in either direction to advance or retard the initial timing. I would suggest only loosening the bolt slightly. This will allow the distributor to move gradually. If the distributor is too loose it may not stay in place when the engine is running and you could move the ditributor way too far. This could stall the engine, making it hard to get the timing back to where the engine will start.
Next are the steps for checking and setting the timing after the engine is warmed up.
#1 Connect the timing light to the #1 cylinder, make any other connections the timing light needs such as a connection to the battery to power the timing light. #2 The distributor slightly loosened in the engine block. #3 Any vacuum hose on the distributor disconnected and plugged. #4 Make dam sure everything is out of the way of any moving parts, such as fan belts. #5 You can now start the engine, AGAIN BE CAREFUL to make sure everything is out of the way including yourself. It's easy to get in the way of the fan or belts while you are trying to see the timing marks on the engine. Don't ask me how I know.
With the engine running, aim the timing light at the timing pointer and look for the mark you made on the crankshaft pulley. The pointer should be near the mark you made at the TDC mark. A general setting for intial timing is about 6 degrees BTDC (before top dead center). This should be a safe setting and is as specific as I can be. You might be able to find a sticker somewhere under the hood telling you what the timing should be set at depending on the age of the truck. Today several stickers can be found under the hood of your daily driver. These are for information required by the EPA etc.
6 degrees is usually 3 marks from TDC, 2 degrees per mark. If you feel the need to change the timing, now is the time to slowly and carefully rotate the distributor ever so slightly. One direction will advance the timing and the other direction will retard the timing. Be aware there is plenty of voltage going through some parts of the distributor. If you end up touching the distributor in the wrong place such as on a spark plug wire or possibly somewhere else you will know right away what 40,000 volts feels like, again don't ask me how I know !! You should see the timing mark  move on the pulley in realtion to the timing pointer on the front engine cover. What you are actually seeing is a strobe light flashing at the exact same time as the spark is traveling through the spark plug wire on it's way to the spark plug. You will probably also notice the engine idle speed change with the timing.
When you have the timing set where you want it, you can stop the engine and tighten down the distributor hold down bolt, it's that simple.
Total timing is normally not changed. It is calibrated when the engine was designed and usually not changed during the life of the distributor. The exception to this would be if the other advance mechanisms inside the distributor failed. For example if part of the ditributor rusted in place the total timing would not be reached. Total timing is also known as "full advance". Full advance is usually reached by no more than 3000 rpm and usually sooner. The timing on my engine has about 34 degrees of full advance of which 10 degrees is intial timing. Full advance is reached by the time the engine is up to 2500 rpm.
You can check your total tiiming by accelerating your engine to around 3000 rpm with the timing light again pointed at the pulley. I would expect any engine to have at least 25 degrees total advance.
Finally why does an engine need timing advance in the first place ? I thought the spark occured at TDC starting the power stroke of the engine. Good question I'll admit. Timing advance is needed so the fuel mixture in the cylinder gets a head start on it's burning before the piston reaches TDC. This way when the piston is at TDC it wil have the full force of the fuel mixture explosion/burn pushing down on it. At idle the piston is not moving very fast and the fuel mixtue does not need much of a headstart on the piston. At higher engine speeds, the fuel mixtire needs more of a head start, so the timnng needs to be advanced further. Again the additional advance is all done by different parts inside the distributor which normally requrie very little if any attention.
So to repeat, if you have a good reason to change the timing and have a timing light, go for it. Watch for moving parts and high voltage.
Checking and setting the timing is a relatively simple procedure. Attach timing light, start engine, check position of timing mark, move ditributor as needed and re-tighten. Simple but very helpful if someone shows you the first time.
I hope this is not too much information and helps you out. Feel free to ask for more info and consider some reading material such as Classic Truck or other magazines realeted to the truck and car passion. Take Care  

Here is a shorter answer:  Total timing = initial timing + vacuum timing + mechanical timing.  Initial timing is the initial state (usually BTDC) that you set by turning the distributor and checking with a light.  Vacuum timing (some use it, some do not) is addition timing added under part throttle conditions by a vacuum canister (mounted on the distributor). Mechanical timing is BUILT INTO THE DISTRIBUTOR and controlled by pins/holes/slots, limiting or allowing a certain amount of timing out of the distributor.  

TOTAL TIMING is the addition of all three (or initial + mechanical) and is typically only present at 2500 RPM and up (maybe more or less, depending on your ignition curve). Example: I have 10 degrees initial advance + 26 out of the distributor and no vacuum advance on my sbc, so total timing is 36 degrees at WOT.

Depending on your driving environment and engine parts combination and preferred "manners", one may use various combinations of initial, mechanical and vacuum/no vacuum advance timing.  You may also have the distributor "recurved" or (example MSD) some allow you to curve yourself, with different weights and springs, to get the timing in earlier or later, and more or less mechanical timing.

roomor