I figured since im a little older and ive been on T for about 7 months now, i should do my part to help my fellow transmascs who are a bit earlier-on in their transition :)
Some of these tips you may have already heard before, but ill do my best to include new information or more specific tips. None of these things are really necessary, your life is your life and you should live it however you want to! But some of these things may be helpful to look more cis, which usually helps you pass better on a day-to-day basis.
Hair:
If you are able to get your hair cut, that's great! The most common haircut for guys is longer on top and shorter on the sides. When you go in and the hairstylist asks what youd like, you'll have to say a magical incantation to ensure that they dont give you a pixie cut. Try this one: "Id like a masculine haircut, longer on top and shorter on the sides. Id like the sides and back to be shaved with a 4 (4 guard), and i would like the back squared and the ears cut out. No pixie cut please."
Getting a masc haircut is kinda like ordering a coffee; they have special names for everything, like "squared" or "4 guard." "Squared" means that they will shape the hair on your neck to be square. "Ears cut out" means that they will run the razor around your ear so that the hair doesnt poke inside your ears. "Guard" refers to the things that they put on the razor to determine the length. 1 is incredibly short and 8 is pretty long. 4 is a good medium length, i dont recommend going longer in this case because it makes it easier for the stylist to make it into a feminine style.
PS: the razor will be loud, especially when it is close to your ears. It will not hurt you, but be prepared for the loudness. Also the longer you have the top portion, the more feminine it will look, but thats up to you and what you feel comfortable with. If this is your first short haircut, please be very careful when moving your head around afterwards; it will be A LOT LIGHTER in weight, and i hurt my neck quite a lot when i got mine cut.
Here's something that explains what makes a pixie cut look feminine vs a mens cut: "The difference is usually that men’s haircuts are far less texturized and have shorter bangs than the traditional women’s pixie cut. Men’s hairstyles tend to be very short at the back and sides, and slightly longer at the top. Women’s pixie cuts tend to also be very short at the back, but with longer sides and especially the bangs are much longer than the rest." link
If you cannot get your hair cut short, dont fret! This is a common problem. Many guys have long hair, but i wont lie to you, it is harder to pass with long hair. We've all heard the tip about stuffing your hair in a hat or in a beanie, but that can be impractical sometimes (but still worth a shot!). See if you can get your hair cut into a long style thats still more masculine (wolf cut for example). Favor middle-parts and avoid bangs. In general, the messier and grosser your hair is, the more people will say "they cant possibly be a girl, a girl would take better care of their hair right?"
Voice:
Look up voice masculinization videos on youtube!! There are voice training videos out there for how to make your voice sound deeper and more masculine. I cant recommend this enough, so much of someone's voice is dictated by just how they hold their mouth, how much air they use, how they hold their throat etc. These videos give explanations and exercises that help you get a feel for a different way of holding your throat/mouth. This will definitely take practice though, its hard to adjust to that as your Default when youve been speaking a different way your whole life. Be patient with yourself! I recommend practicing in the shower, and saying "umm" before speaking to people to give you a second to switch to your Man Voice.
Shirts:
Sleeve length is so important. If youre wearing a tee, your sleeves should go down 3/4ths of your bicep or almost to your elbow. Dont go past your elbow, youll look like youre drowning in the shirt. Also, i prefer for the waists on my shirts to be a bit long (mostly covers the crotch, but doesnt go past it). I like how shirts from skate brands fit me! Although skate brands can get quite expensive. You can find good shirts elsewhere too. Always buy mens or unisex.
As for colors/patterns, try grey, black, red, dark green, navy, or any dark neutral. Graphic tees are good as well, as long as the base shirt color fits the colors i just mentioned. I would say to avoid patterns, but otherwise i think smaller patterns are better. Avoid stripes, grids, or polka dots. Try goodwill! But dont hoard, remember that other people shop there too, and always donate your old clothes back.
For shirt collars, you absolutely need to cover your collarbones. Something about a wide-neck tshirt will absolutely slaughter any chance you have at passing. Look for the words crew neck.
Also avoid tanks, mens tanks have enormous arm holes that will show anything youre wearing under, and womens tanks have too thin straps. If it's too hot, i recommend getting a tshirt that you know fits you well around the collar and waist, and cutting the sleeves off, as tshirts should have normal-sized arm holes.
Pants:
When i was first starting out, i always wore joggers, but that was because that was what the boys at my school wore. Have a look around and see if any of their styles catch your eye. Otherwise, i recommend a good pair of jeans.
Guidelines for jeans:
Straight leg, medium or dark wash, always buy mens. I like Lee or Levi's. Mens jeans are sized differently than womens, but theyre also more standardized across brands. Mens jeans have 2 numbers, for example 30x34, waist x length. The waist is a mid-rise fit, around your hip bones. I'm roughly 5'4 or 5'5, skin-and-bones, and i wear a 30x30, and thats still a bit long on me. It pools around my ankles a little, but unfortunately, we as transmascs are short. You most likely will struggle with your pants being too long for you. You might be able to fix that with tall shoes.
Shoes/Height:
Converse, vans, adidas, nike, work boots. I actually have a pair of underarmor shoes that i wear constantly that i love. Mens shoes are enormous tho, so heres a hint, wear kids sizes! Theyre cheaper too :)) You should be able to find kids shoes that look alot like adult styles but just smaller.
When i say work boots, i just mean plain black boots. Docs would work fine i think, but you can also find something cheaper! Here's where my tip for height comes in: you can buy height inserts/insoles off of amazon and put them in your boots. They wont fit very well in normal shoes, because they push your feet up and youll just slip out of your shoes, but boots work well for height inserts.
Walking:
Here's one i dont hear other people talk about much: girls tend to walk on a singular line, whereas guys tend to walk on 2 lines or in a box. It's kinda hard to describe through writing, but hopefully thats an apt description. The more you cross your legs while walking, the more feminine your walk will appear. Practice walking with your feet Slightly apart, but try not to look like you have a wedgie. Also, when standing, try not to put your weight on one leg, try to stand evenly. (Tho admittedly, i dont care about that last part, i still put my weight all on one leg, because its comfortable damn it)
I hope i was able to help at least a little! If you think of anything else that you would like me to address, please let me know in the comments!!