After reading the posts, i found some new users searching for power-off troubleshooting tips and most of the info on the site is for advanced huntron users. Hope this helps someone out there.
This is what i do when i have a faulty board.
I start by studying the board , looking for symmetry , repeatability in the circuits.
Next, i look at all the ic numbers on the pcb and find their data sheets, especially their pinouts.
Based on that i try to figure out how the board works or at least get an idea of what it is doing.
I prefer not turning on the power when troubleshooting .
I only power on to check if it works after i replace components .
When power is applied ,i find things get very complicated.
More than 70% of the time ,i manage to find faults in both digital and analog circuits just using trackers to spot differences.
If all else fails ,then i power on to do some functional testing ,test with multimeters ,scopes and other instruments; looking at board calibration ,function etc .
Nowadays I start testing all electrolytic caps first with an esr meter. The rest i look at with a tracker. High stress high heat components are tested first ie those on heat sinks,then diodes,transistors in that order, all the time carefully looking for burn marks or any telltale signs of physical damage.Any socketed ics eg memory,i take out and check their firmware on a programmer.
I always try to get exactly the same boards or modular boards to compare against. I am from the time where data storage did not exist,so i got used to realtime comparisons....it has worked well for me so far. I don't spend a lot of time learning signatures into a database for comparisons.Nowadays storage is the way to go ! Storage has advantages ,you CAN store data sheets,pinouts ,photos ,videos ,testing notes (like reminders) , and other symptoms observed and link them to signatures, so you don't have to search for them every time.Also when people leave the company ,their work done ,info gathered and other data does not leave with them.
When using huntrons , i find 3 ranges is sufficient... too many ranges only leads to confusion without increasing my chances of "seeing" faults.
I think of trackers as "xray machines" for electronic circuits. A doctor would ask for an xray of his patient if he needs more info . Symptoms are good but Xrays are better for accurate diagnosis. In the end its all about what we can see and analyse to help increase our observation and diagnostic skills ....Signatures "talk" to me because i am confident that when electronic circuits fail,they fail at the input -output pins. They go open or low R when they have been stressed ,either by the circuit design or by something external .
I keep all the faulty components i have found over the years... building up my trophy collection

When i have time i plan to post pics of my fail ic collection for the benefit of everyone.The idea is once you see what failures look like on trackers,it may help you spot them when you are trying to find them.... its a good study on how components fail.
To sum up ,when troubleshooting ,I like to use something simple to see the fault. Huntrons allow me to see more with their current limited AC, compared to multimeters with only DC.They also will not damage the board i am trying to fix. I do not have to worry about polarity while probing, which saves me time.
Using huntrons CAN be addictive, once you use it ,you CAN'T live without it.
Hope this helps , happy probing!