Ooh, cute UPS guys in shorts.
Shoulders, and the angle between them and the hips. Then butt. I won’t say I wouldn’t look at a crotch, but it’s not the first thing I’d look for.
In order: eyes, smile, hands, general movement (by that, I mean confident movements or jerky, unsure stuff (yuck).
I would definitely check out the rear view given the chance.
The set of his shoulders and how well his shirt fits those shoulders. Yes, even T shirts. I do not like overly “ripped” or built guys-major turn-off for me.
After that, hair, smile (teeth-does he have them and are they clean?), height, weight, degree of hygiene, choice of clothing/tattoos (ugh)/attitude. Most things are negotiable, but a 'tude is not.
Boy oh boy, can I ever relate to that. A tattoo playing peekaboo under the sleeves/collar, or a subtle piercing on an otherwise conservatively dressed man are guaranteed to get me hot and bothered.
Ditto on a faux hawks or any other sign that there’s a naughty naughty boy somewhere under the stuffy exterior. It just makes me wonder what else is hiding under all those clothes. 
Mmm, t-shirts. I love standing behind a guy with great shoulders in the summertime - then I don’t mind a slow line in the supermarket at all. 
'scuse me, I’ll be in mah bunk.
Placement of facial features, profile, hair, eyes, lack of flab or knobbyness (so nobody is safe! however, such things are not deal breakers), distinctness, carriage, and whether you look friendly or not. I don’t care all that much about asses, limbs or height ('cause I’m short). I’d never “check out” a bulge, but admit that a prominent one will probably force me to briefly consider you in a sexual context, for better or for worse.
Obviously the first criteria is cleanliness. If a guy looks filthy or smells rank, I’m going to be getting the hell away from him ASAP. But assuming he doesn’t stink and looks clean…
In order: eyes and eyebrows (I like interesting eyes), smile, hands, nose. Then clothes and hair.
Then how the guy moves - I’m a sucker for fluid movement; I don’t like the muscle-bound heavy athlete walk.
Crotch package doesn’t make the list - but then again I’m not really sex-driven, so that’s probably to be expected.
[ETA: For what it’s worth, weight isn’t an issue. I dated a guy who was over 150kg but did ballroom dancing as a hobby and was very light on his feet and moved beautifully. If he’d clumped along, that would have been a dealbreaker, but not because of the weight.]
Things I check out:
When they lick their lips
Their walk
The way they stand
I love a very young guy with a full beard…like to watch when they stroke it
Like to watch them eat
If they ‘grab’ their bulge, I will notice and check it out. Otherwise, I rarely look there
I never check out a guy’s butt, but I do check out girl’s butts. If a girl has a big* but and round hips, I check her out. I blame my husband. He really has given me an appreciation for a well built ‘thick’ woman.
*big = ‘butt bigger than gut’…round, not just wide and flat.
It depends. If he has a “bic’d head”, I will always notice that first. Something about a guy that shaves his head bald. Yum. If not, it’s always his hands. I am not sure why, just do. Then their smile. Laugh. The way they handle themselves is big to me. If stands strong, stands confident; huge turn on.
A guy with tattoos. There are many things that I like, but the bald head thing always turns my head.
Oh, yeah. Tattoos are nice. Most guys I like are too black for tattoos to show up. But I have noticed that the guys I like that do have tats that show up are a real turn on.
And scars. Love those. And a chipped tooth.
Lips.
Ass.
I notice eyes and noses most of all facial features. I like really big noses (like Adrien Brody big noses!) and light eyes with dark lashes (Jake Gyllenhaal, Cillian Murphy.) I like tall lean men most, but muscley ones will catch my eye as well as long as they’re not total gym-monsters. Butts for sure, packages if they’re the type that stand out to be noticed because I’m a bit of the size queen–sue me! A well turned calf or thigh makes me go bibble-bibble… Another thing that’s pure sex to me is a guy shirtless wearing jeans or shorts that come down a little lower than usual, showing that flank area that V’s down to the crotch, whew! I used to really like the hair farmers and a well tended head of long hair or a ponytail will still draw my eye, but I’ve really come around to appreciating very short spiked hair or even baldness on the right guy.
I’m totally shameless about ogling the younguns–they’re so damned pretty! It’s like admiring a litter of golden retriever pups, they’re that cute…
Face. After that, arms are good. I like skinny guys, but a skinny guy with toned, muscular arms beats a skinny guy with scrawny arms. Weird, I’ve never thought about it that way before.
(Oh, and have never, ever checked out man-bulge. Ew, creepy…!)
Eyes, definitely, then their smile and accent. I’m a sucker for accents.
If in view - Butt first
Second - smile/teeth
Third - arms/shoulders
Of course, this is removing all non-physical attributes that can quickly override any of the others EXCEPT for the teeth part (they have to be decent, even if it’s a set of dentures)