Wes to assess a trophy deer that runs 150 or better it will take a bit of time, although when they are truly big not much will stop you either. For me I look at all characteristics of the antler make up:
a) Beam Length -24" is want your looking for on a 150 + class WT (I want to the nose with a nice sweeping beam or high past the nose with the tight rapper beams)
b) Spread 2" of daylight on eitherside of the ears will put you in the 18-20" spread depending on his crown. Also make sure you note if his ears are straight or slightly cocked, this can really throw you off.
c) Tines - number and size When looking for a 160 class buck you'll need 5 a side, now their are expection but that will fall into the "Truly big not much will stop you" category. I look for the stair step and wall(which also indicates mass to a degree). Basically on our mature bucks from the eye to the tip of the nose is 9", put the tines into that spot in your mind and you'll be able to guess how big each tine may in fact be. You'll want G2's and G3's to be double digits to make 160 or better - magic number is in that 12" range for G2's or G3's - don't be alarmed as many will exhibit larger G3's than the G2 position, perfect if he's got 12" g3 and 10's for G2's, if the others fallow suit down not usually much need to count the bottom 2 or brow in your mind.
Symetrics is nice but hard to really judge, unless really lopesided I don't let it bother me much nor do I have time to try and guess at a net score.
d) mass most deer that exhibit some of the traits listed above will have decent mass, exceptions of course apply for loads of mass and spindly tines.
Finally Nontypical, I am a sucker for these deer and if I see one that just looks right I rarely field judge and just pull the trigger to find out the results. I am not talking a kicker here or their, but rather a deer that exhibits unusual growth that just looks to darn good to pass.

I know so much for the quick and easy method but probably the best judge is the man behind the scope, not everything is in score when you see him if he just looks the part and you'll be 100% satisfied with him mounted on your den or office wall then you have been affirmed...not only that I have seen guys nit pick a 160 right out of their wall by not going with that gut instinct on first sight. Your doing the right thing look at mags and videos of these big and small deer. Whole doing so try to pick out features that elude to a trophy animal. Not one element but several, b/c as mentioned you need to truly measure every inch in a very short moment to come up with a decision of safety on or off. I may also say do not be affraid to ask your outfitter or guide for tips on judging the deer.

Best of luck and sorry can't help you with your outfitter on his rep. I am sure you called his reference list and chatted with previous clients before picking him? If not then I suggest you do, so you know what to expect when the plane lands! These folks can also be help in your quest to field judging deer.