The biggest thing is you want to make sure the vale you are adjusting is closed.  If you adjust the intake valve when the exhaust valve just starts to open you'll know its closed.  Then adjust the exhaust valve when the intake starts to close. 

I'll add that the spin the pushrod method of making sure the clearance is all gone has never worked for me.  I move the pushrod up and down instead.  Every time I tried the spin method they ended up too tight. 
 

Greg B wrote:

It gets confusing when people adjust lifters that have not bled down. That is how valves wind up getting adjusted too tight.

Take a new lifter and push downward on its innards. You will see it compress a slight amount. This is what is translated to the "half to 3/4" nut turn after zero lash. when the engine is running hydraulic pressure keeps it tight. You do not want it bottomed out, nor completely topped out.

I used to have a great picture poster that explained how they work and how to properly adjust valves on my garage wall. I wish I still had it. It was the best simplistic explanation ever.

Yep, I was going to readjust/check the preload on my lifters. I believe the preload was to try and center the plunger half way into it's self adjusting range. In order to do that you would need to have that plunger in it's upper most position first. I was wondering how to make sure that the plunger was at it's upper most position? I'm thinking the spring inside the lifter returns the plunger to it's preload position when a valve is closed? Intake is on so I can't see the top of the lifter.

Greg B thanks for the video add. Very useful

 

If the lifters are already filled with oil, it will still work.
The spring should push plunger back up.

The first and most important step is getting all to zero lash.
Then add the 1/2-3/4 turn.

Last time I did this on the 289, I used the firing order method.
Placing each piston at TDC and setting to zero lash.
Then I added the additional turns.

This video came out many years later.
It would have saved me time and frustration.
I was trying to follow the confusing procedure in my Hanes and Chilton manuals.
Firing order made the most sense to me.
I could see both valves closed and then set zero lash.

If you prefer to have the oil bleed out of lifters:
Rotate engine manually at least two full revolutions and all lifters should compress easily