I leave my strings tuned. Never turn more than 1/8 turn at a time. Directions can be confusing so leaving the strings tuned allows you to use an electronic tuner to see if you're loosening or tightening. Besides that, you can also quickly check to see if your adjustment is enough, not enough or not even close, without having to constantly retune. You shouldn't have a problem as only a 1/8 turn on the rod will quickly show up in the string tuning and is no where near enough to cause any problems.

I leave mine tuned but it's always wise to wait awhile before making more adjustments. Sometimes it takes a couple of hours for the neck to really "settle in" ..

As an aside.. You only adjust the truss rod to put in /take out neck relief. NOT to generally "adjust the action". If you want to change the action on the guitar saddle/nut is your best places to start.

Thanks for the info, gentlemen.

>>You only adjust the truss rod to put in /take out neck relief. NOT to generally "adjust the action". If you want to change the action on the guitar saddle/nut is your best places to start.

Yeah. Because it's an acoustic, I don't have any bridge parts to adjust. The guitar is about a year old so the nut is A-OK.

The deal is that she has been sitting in her case for a few weeks. I have a junker acoustic at my rehearsal space that I have been banging on. Last time I played her, I meant to put the humidifier in the case, but forgot. Chicago has been sub arctic cold this winter and my apt is bone dry, so earlier this week I opened the case, put in the humidifier, and closed it for a couple of days. When I pulled her out last night, the action seemed a little high and the neck looked like it was bowing forward. Because I was strapped for time I figured I would make the adjustment tonight and give it a day to settle in.

In my opinion it's safer to loose the strings a bit.
When You adjust Your guitars neck, forces that are created
by truss rod are really big, the wood need to "rest" and shouldn't be tensioned.

I keep my guitars tuned. In a similar discussion, the old G.com elite (guitar builder included) also agreed on keeping the tension on. But as said, it may take time for the neck to settle. It will take even more time the farther away the neck is from its balance point, like when you adjust while detuned.

"Because it's an acoustic, I don't have any bridge parts to adjust"

Actually, you can take the saddle down a bit to adjust the "action" but, if the neck is bowed I would do two things.
First I would put a humidifier in the case and keep it closed for about a week and see if that helps.. If not, truss rod adjustment is probably the answer.

How do I know if I have trussrod?

You'll know by looking on Your guitar's peg-head. If there is a cover, remove screws and look.
If there aren't truss rod cover on Your guitars peg-head -> You don't have truss rod.

If You meant how do You know if You have problems: just play Your instrument.
If there are problems You'll feel the bad action.