There is, at the local Wal Mart,  a guy working at corralling carts in the parking lot.  This guy would be a fabulous model as he has the looks of a California surfer: longish blond hair, tanned face, and a good looking body shape. This guy could easily be a model for Abercromby & Fitch, Hollister, American Eagle etc..  Any suggestions how I could approach him and offer to do a shoot with him? I am a naturally shy individual and don't want to sound like one of those creepy photographer types.

Its really simple. In a public place tell him you are a working photographer and think he might make a good model. Would he like to let you photograph him.

He simply says yes or no.

That's all there is to it. Be open, honest and see what happens. How could anyone be offended by a sincere compliment?

Tell the person you are a photographer, think they would make a good model, give them your business card with contact information and link to your website.  Tell them to take a look at it, think if over and contact if you if they are interested in modeling.

find a pretty female assistant to do it for you

Do  not put anyone in a position where they have to give a response right now.  You've been thinking about it for a week.  They haven't given it a single thought.  Give them contact info and an internet link where they can see your work.  Let them think about it.  Introduce yourself, be professional, give them a card, walk away.

Have a card with a link to your website where he can see your work and contact you.
Introduce yourself, let him know you're a photographer and ask him if he'd ever considered modeling - don't hang around invading his space to talk - tell him to take a look at your work and contact you if he's interested in shooting with you.

Easy. I used to do it all the time when I was first starting out.

Don't over-think it - in/out/done.

Lots of people 'should' be models but don't have an interest in modelling.  Lots of people have the look when they're out on the street but somehow lose it when they're in the studio.  Lots of people should be models, but never get the breaks.

Be careful what you say to the guy.  Don't try the " You could easily be a model for..." line on him.  Offer him money for a shoot, say you need someone with his look for a particular job or project.  Offering a TFP shoot isn't a particular incentive for someone who probably won't have any use for the pics.

And make it casual.  You approach lots of people in the street every day, or so he must think.

Business cards work best - keep it brief.