I've seen a lot of questions on how to better communicate to your duo partner more 'tactically'. The good news is no one yells out shit like TANGOS in DELTA, CHARLIES in teh TREES!!!!!!
The most important concept about effectively communicating in a combat situation is keeping it simple. If you begin by throwing out all kinds of insane terminology and descriptions 1) you're brain isn't in the fight anymore and 2) you're confusing the every living fuck out of your teammate.
The 3 Ds
Distance: Simple range that you're teammate can understand, can change on the situation.
Direction: Changes depending on where you and your teammate is looking. Tools to use, Compass at the top of your map. N,E,S,W are very broad terms but usually enough to get your teammate on target.
Description: This is up to debate. I suggest to keep it as simple as possibly while giving enough hints to where the target is. Large red barn, blue roof.
Now to what this should, or could sound like.
"Hey we're just talking about stuff, whats your favorite pizz- Ah shit, guy 100meters from me SE, he's running our direction just passed the gas station."
"Do you see him" 'No'
50m from me now, i'm going prone, he's between me and the nearest building now
'Alright i got him'
Distance 50meters, 100ft, 200m, 300m, 100 yards
At long distance don't try to narrow down below 100yards/meter increments. At those distances 10-20-30m distances will blend into each other and the small increments won't do much for you.
Direction Compass directions are very general directions to get someone facing the correct way. Once they are looking the same way you are USUALLY distance/description will be enough for your partner to find your target. If the target is prone, or stationary you may need to be a little more precise. The numbers you see on your compass are in degrees. Starting at 0 all the way up to 360. Just remember degrees are relative. They won't help your friend much if hes 150m behind you, but if you're close they'll give him a better idea of where to look. The close you are the more accurate your directions will be. (but never be too close, for other reasons)
Description Imagine you're explaining to a 4 year old where you want them to look. Enough information to differentiate 1 building from the rest but not enough to for a forensic investigator to draw a profile of the perp. 2-3 descriptive words should be enough.
2 story white house with the blue roof. Large rock outside the tree line. Second hilltop from us. 4th tree from the west.
Bonus advice to sound like the pros. If you really want to role play and get into character you're going to want to stick to the 3 to 1 golden ratio. 1 swear word for every 3 normal words. Good hunting!