how to rent an apartment or unit?

Hi,

i want to rent my own room/unit.

1.
can i talk directly to the landlord of the apartment? or i need to contact an agency first?

2.
I am a gaijin, and im a little nervous that the landlord might not want me to rent his/her unit, should i bring someone from the office i am working at?

3. what are the requirements for me? or what do i need to have before renting?

thanks in advance

Please check this page if you haven't.
http://www.japan-guide.com/e/e2200.html
Yes, we normally use real estate agencies to help us find a room. Unless you know the landlord directly/indirectly, it is very difficult to find a room on yourself. And if it is possible, I recommend bringing someone (Japanese) to the agency with you.
It is good not only for making it easier to communicate but also to see the room from a different perspective.

Hi Charlie

I've rented an apartment through Sakura House before.

They are gaijin friendly, and don't charge all that 5 months in advance key fee etc stuff.

Check them out - their website is in english.