Let me begin from the bottom...
Any kind of hiking, trekking option is a total no-no, unless you are (obviously) hiking somewhere in the nature and everyone around you is dressed in the same way. Which is completely appropriate, even desired.
Crocs are instant deal breaker. I am very strict about this particular piece of horror. If it was up to me, I would force people with Crocs pay some sort of penalties, although they are being worn just around the house for gardening section. No. No. No.
Trousers, jeans, pants
First and probably most important is the length. Pants are not supposed to dance freely around your ankles. Ankle length is allowed with skinny tight pants (you know, the version seen mostly on hipsters), and even in this case they cannot move around the ankle since they completely wrap your legs.
How high? What? How high is you waistline, I mean. Gentlemen, please... If we can actually see your family jewels while standing straight (one ball on each side hanging over a male version of camel toe, or both on one side - I can't really decide which is worse), get rid of these pants. Immediately if not sooner.
Upper body clothing
There is a whole variety of clothing worn as a top, so I am just going to point out the most critical mistakes men make.
Fancy shirt under a sweatshirt. What, you're going clubbing after gym, or straight to the hills after party? I am not really getting this combination, and - as it seems - no woman does.
Sponsored t-shits. You can wear them for cleaning, repairing your car, running, waking your dog, just being at home... but, please, for the sake of our innocent eyes, do not wear them under any circumstances on a Friday night. Thank you!
Ok, these are some basic instructions or, better yet, guidelines to follow. For detailed manual talk to you girlfriend, friend or even mom (that can be critical, so be careful when taking this path).
Fashion fades, only style remains the same.
- Coco Chanel