What is the best medium to educate doctors? newsletters, conferences,
face-to-face meetings, etc?

Medical School, perhaps?

Educate DOCTORS...which means they have already attended Med-School. 
I mean if I were trying to educate Drs. on a new product and the
clinicals trials surrounding it.  Not like a pharmaceutical sales rep.
 but from a PR standpoint. If I was tyring to publicize an event for
doctors - where would I go, start with newsletters, or conferences,
etc.?

Oh, you're not trying to educate them.  You are trying to advertise
your product.  Advertisement does not equal education.

If you read the question that was asked, it says what medium would be
best such as conferences, newsletters, etc.  I do not have a product
to advertise.  I am just trying to find out, in which way i would
reach the most doctors.  That is all.  Not advertising for a product.

Mostly it is done with an extensive salesforce
- freebie conferences
- and blatant bribery

There are medical conferences that you can get your
product/information into.  This will not hit the most doctors, only
those who go to the conference and actually look at the exhibit
though.  Probably the best way to get doctors to actually try
something or change their practice is to go to a teaching hospital and
talk to one of the more respected doctors to listen.  If you convince
them there is a much better chance of word of mouth between docs
getting them to start doing whatever you need.  Plus you get all their
underlings on board, who will go out into practice on their own soon.

Just plain reaching the most doctors would be in a magazine like JAMA
or the New England Journal of Medicine, although ads in those are not
really looked at for the most part.

You might want to do research related to the Pharmaceutical Marketing
Science Association or Pharmaceutical Marketing Research Group.  On
their sites, you may find conference presentations that will present
benchmark data on promotion response effectiveness of different
channels.

These comments are based on working in a hospital as an administrator.
Educating physicians is going to depend if you use a "push or a pull
mechanism". Often times they are very busy and pushing information,
data or education is more successful than forcing MDs to go lookup
something.

If you do choose to have meetings or conferences, getting physicians
to show up is essential. (Trick: Offer food.) Is whatever you are
trying to educate them about, something s/he can earn Continuing
Medical Education Credits? If so, advertise it like so.

If it is a product that would be used in the doctors office, I would
suggest you approach the office manager and get his/her buyin.