How to decide is a word is in its noun of verb form

Noun. If you can say 'a conflict' or 'the conflict' it's a noun.

Thank you

Is it always as simple as that rule you have quoted there?

I need to adjust the sentence slightly.. If presented with "Those two are in apparent conflict" Is conflict in its verb or noun context?

The only change is the removal of 'an'

How would you use conflict as a verb, in view of the fact it's not one?

You can use any noun as a verb, it all depends on context.

Yes it is still a noun. The example you've given is an awkward one - it's not a sentence I'd ever say. But you are talking about a state rather than describing an action. If you continue on... 'Those two are in apparent conflict. The conflict was caused by a disagreement over money.'...then it perhaps becomes clearer that it's a noun. In love, in fear, in doubt, in apprehension....etc

Your assertion conflicts with the evidence:

http://dictionary.reference.com/browse/conflict

Your meaning is clear, but your sentence is ungrammatical. That's a very silly reference imho.

The two armies conflicted with each other, until they got tired and went home.

My sentence might not be something I'd say in everyday conversation but the grammar is just fine. Even if you think definition.reference.com is a 'silly reference' I think most people would accept Merriam-Webster and Oxford dictionaries as fairly reliable sources and they both agree with my usage. I think you will struggle to find a dictionary that doesn't have conflict as both a noun and a verb.

http://www.merriam-webster.com/dictionary/conflict
The expectations about motherhood as full-time job that this situation created conflicted with the philosophy of the women's movement of the l960's. —Anita Shreve, New York Times Magazine, 2l Nov. l982

http://www.oxforddictionaries.com/definition/english/conflict
the date for the match conflicted with a religious festival

I think I'll concede this one, with apologies. I'm aware of course that you can table a motion or boot a football. My Oxford Concise does not have "conflict" as a verb, but plainly it can be so used in certain circumstances. Indeed we have different pronunciations, with stress on the first syllable for the noun, and on the second for the verb.
My bad.

Your graciousness is a rare quality around here and something I can probably learn from myself. Thank you.

Those two dates conflict.

Those two days are in conflict with each other.

Or you can hammer a point.