Every tackle shop in the country has a collection of carp rods in stock, what you've got to decide is what you want from your new rod.
Do you want to cast a long way? Or do you want to fish close-in to the margins?
How powerful do you want the rod to be? What action?
Will it fit in your holdall? Will it fit your reel?
How much do you want to pay? At last years Chatsworth Angling Fair, tackle dealers were selling carp rod and reel combo's for only £10. OK so they weren't the best in the world, but they would get you started!

Test Curve
This determines how powerful the rod is. In theory a 2.5lb test curve rod should be bent through 90 degrees when a 2.5lb weight is attached to the tip. I've never risked it myself, but it gives you some idea how beefy the rod is.

Action
Fast, tippy or stiff actions all mean the rod has the power to cast a long way.
Soft or through action means the rod is more suitable for margin or medium distance fishing. They tend to be more forgiving and flexible, reducing the risk of pulling out of a fish.


Quality Issues
Line Guides - The fewer line guides the less the resistance there will be on casting, so if you are looking to hit the horizon, fewer is better...usually a carp rod has 6 to 8 guides.

Check all the guides to make sure they are up to the job, any that are fragile, cracked or loose should be discarded straight away. Check for guide alignment, do they all line-up down the length of the rod?
Check the varnish protecting the whippings locking the guides onto the blank, any whippings not completely covered by varnish can soon rot.

Joints - Make sure when the rod is assembled, there is no looseness or wobble. The joint has to be a snug, secure fit with no weaknesses. Ask someone to hold the rod tip while you put a bend in the rod, make sure the rod bends in a nice smooth curve, without it creaking.

Handle - Is the handle comfortable, is it long/short enough?, does it fit under your arm, I've had to cut 6 inches off the butt end of my carp rods to make them more user friendly.
Will your reel fit? There's no use in buying a rod when your reel won't fit it securely, check it first!

And finally - a suitably sized rod tube is a good investment to protect your rod during storage and transportation, they only cost a few pounds, but are well worth the cost.
The addition of a circle of foam glued inside the ends of the caps will add even further protection.