As far as resume format:

Here’s a link that I made to illustrate what I’m going to talk about:
http://i707.photobucket.com/albums/ww80/ELDORADO59/scan0002.jpg

RESUME-ALWAYS use the 3 column format!
Here’s the standard LA format. In NY, it’s usually the same but with Theatre being higher up than Film/TV (/ denotes column breaks):

At the top and centered:
Name (Centered and is largest in font size)
Union affiliation (if any)
CELL Phone Number
Email

Far Left side below the top and centered stuff:
Height
Weight
Hair color
Eye color

Right side opposite of statistics:
Agent logo with contact info (sometimes if you have an agent, you can remove your own cell phone and email address. Then weirdos that find your stuff in the dumpster can contact them instead of you)

Film
Title/(Lead, supporting, featured)/Director

Television
Title/(Lead, guest star, co-star, regular, featured)/Network

Theatre
Title/Specific character played/Production company or director depending on who is more prestigious.

Commericials
ALWAYS put "List available upon request!" Do keep a separate list of the commercials with the Casting directors involved in case an agent asks.

Training
Skill learned/School or teacher/Location (LA, NY?)
OR
Skill learned/Teacher/School Location
ie. Cold Reading/Margie Haber/Margie Haber Studios, LA,CA

Special Skills/Abilities
Be creative with this. When I was starting out and interviewing with agencies, they would usually go straight there and talk about my special talents and even had me demonstrate some of them

DON’T:
-Put extra work
-Put Modeling/Print gigs. You make a separate resume for that.
-Lie
-Put age. If an agent asks you when you meet with him or her, then tell the truth. It’s for legal reasons. ie. Under 18 can’t work normal hours or you have to be at least 25 to do a beer commercial.
-Put your home phone number or address unless you want weirdos coming to your house.
-Put dates. It ages you!
-Have it separate from your headshot. It should be cut to fit and stapled to the back of your headshot.

If you don’t have too many credits or none at all, have a lot of training. That will show that you’re still serious. Also be creative with your special skills and abilities.
References :

Show——Various Roles——Where or what company or director

Instead of various roles you could just put Lead or Leading Role OR you could just put the most recognizable role.

Example, I was in Annie and I play a cabinet member, servant, and "hooverlite bum" …so to keep things looking neat and simple I put

Annie—–Servant——XYZ Co.

and stuck it at the bottom of the list.

EDIT: Looking at Eldorado’s advice I must point out a few things…
1. Don’t put you’re weight. No one needs to know how much you weigh it’s not a wrestling weight class division.
2. No need to put eye color or hair color if you’re attaching a Head Shot. You’re headshot will be color and therefore telling them what you’re eye color and hair color is. Back when actors used black and white head shots, that information was important. The times have changed. (this is advice coming from an agent)
3. The resume format he gave you was god aweful. Too many things to criticize so I’ll just link you to a great looking resume: http://www.johnvirag.com/jv_images/ActingResume.JPG

That’s not my resume, but it’s format is perfect. Mine looks similar but my theater credits are at the top instead of film since I’m predominantly a stage actor.
References :
I’m an…. actohr!!!!!! rawr!!!!