Critical items for a ride

[Trader914]

I own a Ninja 250 which does not have any place to carry anything. The only space available is under the saddle that holds a small tool kit that came with the bike.  If you were going on an afternoon ride (not overnight), what are the most critical items you would carry on the ride?  The only space I have is few pockets I have in my jacket. Also, are there any seat/tail bag/luggage you would recommend for a bike like this?

[Yard Sale]

Magnetic tank bag works great on a Ninjette's flat tank.

[Trader914]

But actual items do you think are important to take with you on every ride? I always carry my cell phone and wallet, of course.... What else would you take so you will not get stranded?  A month ago, the bolt that holds the gear shifter fell out of the bike.  I was able to actually find the bolt on the street (I was at a red light when I noticed) but I did not have the correct allen key to screw it back in. I had to improvise to get home.

[Yard Sale]

Tools, fuses, tire plug kit. A spare clutch cable zip-tied to the clutch cable.  Maybe spare levers in case of a crash.

[Justin]

Most important is the Emergency Information card.
Which should include your name, DOB, allergies, medications, medical conditions, physicians name and telephone#, blood type and the name/#of your emergency contact.

You gotta go through the bike regularly.  Preventative maintenance will keep your stuff attached.  Go through the bike carefully with a compliment of hex keys when you clean your bike or clean/lubricate your chain (every 200 miles)  One bike I owned had to have lock-tite applied to every bolt, or else it kept getting lighter. 
Cables and brake/shift levers are a great suggestion, as is the magnetic tank bag. I usually have a spare visor/plexus and a microfiber towel with me.
    I have roadside emergency service from both AMA and my insurance carrier for the bigger stuff.

[Trader914]

Where do you carry the extra shield?
Also... what service do you recommend for roadside emergencies? Somebody told me AAA offers motorcycle towing..and I have AAA.
My insurance will not offer towing because I do not have collision/full coverage.

[Justin]

You should look into American Motorcycle Association membership.  They have a lot of benefits, including fighting for your rights to ride!  I can't remember if the AAA coverage was because I had moto-incurance with them. I used to carry a spare shield in the tank bag.  I like having a spare visor if it gets scratched, or got dark before the end of the ride, etc.