Are you located in the US?
Start with, do you have a Bachelor’s degree?
Have a look around the web on how to write a resume when you are “older” and/or possibly considered too experienced for the job market. How to deal with dating your work experience. How to negotiate pay rates. There are far too many people out there that think they can hire a kid fresh out of school, pay them peanuts, and get Quality work. You’ll probably have to do a hard sell and that’s where a very strong portfolio comes in.
Also look around the web on the plus or minuses of having a social presence online (if I ever have to look for work, I’m screwed as I think most of that TwitFace stuff is a waste of time…)
As for a portfolio, depends on your field, but in most cases people are going to expect your work to be online somewhere. A physical portfolio depends on what you do. For instance, the stuff I build (signage and wide format print) doesn’t fit in a portfolio, would only be photos so an online presentation would probably be fine, with a tablet/laptop presentation as a backup for interviews. Same for web design. Show live sites. For a print designer doing marketing collateral, actual printed pieces that the interview er can see in-hand might be helpful. Et cetera.