% Men
We don't have much information yet about trans men, but you can the Hudson FTM Resource Guide, which contains a lot of useful information.
As a trans man, typically you would (if you were going to transition) take what is called HRT or hormone replacement therapy. This will give you the same estrogen/testosterone balance as a typical cis man.
With HRT, several things will happen to you (this list is not exhaustive):
More information is on this Wikipedia article.
Your mileage may vary! Some people don't get changes, while others might only see some of these changes, or they will see them in varying degrees. It all depends on your body (and what type of hormones you take, at what dosages, etc). All of this depends on age, genetics, etc. There's no telling what will happen to the individual trans person, you just have to see what happens basically.
http://www.ftmguide.org/ttherapybasics.html
Info on HRT for trans men: http://www.ftmguide.org/ttypes.html
We have information about getting HRT on the TransHelp site. See:\ How to get HRT if you're a child/teenager\ How to get HRT if you're an adult\ Private trans care providers\ How to purchase HRT on the internet
You can find these devices online. They allow you to pee while standing up, e.g. at urinals in male bathrooms. You should get a 2-in-1 STP and packer device (see notes about packers below).
A packer is a device that you wear on your crotch, to give the appearance of a bulge, which cis men have when they wear trousers. You can see a bulge from their penis. A packer will give you the same appearance, if you've not had surgery.
Make sure to get a 2-in-1 packer that also has stand-to-pee functionality.
Here is an excellent YouTube video about packers, which all trans men should watch: https://www.youtube.com/watch?v=v2LEh41xTYw
You can get surgery to give you male genitalia, and to remove your breasts.
If you haven't had top surgery yet, you can wear a binder which will reduce the appearance of your breasts. Your wear this under your shirt.
You can use a stand-to-pee device if you want to stand while peeing (e.g. at public urinals) if you haven't had bottom surgery yet.
We have a section for this on the TransHelp site
Very indepth and interesting page that debunks prejudice against trans men.
Sex education booklet for trans men that focuses in the UK but is still relevant for everyone http://www.tht.org.uk/~/media/8F7D70D8C3B643109351E3D9A633529A.ashx
Sex education for gay trans men (trans men into into men)
http://librarypdf.catie.ca/PDF/ATI-20000s/24654.pdf
FTM Sex Talk (Q&A about trans men)