How can I tell which replacement Inner Tube to buy?

I have an Apollo CX bicycle. I have a flat tyre and need to change the Inner Tube.

I have never done this before and so I don't know what to buy. I can take the punctured tube to the bike shop, but I would like to know what to buy. Could someone explain how to get the right size - I imagine the wheel diameter and thickness is important. E.g, the Apollo CX is a Town Bike with slimmer tyres than a Mountain Bike.
Bradley, September 2009


done
look on the side of your tire. it should give the diameter of the wheel and the thickness of the tire.

most likely the diameter will be it will be 26"

and then it will give you a thickness.

I ride a mountain bike (2")

example= http://3.bp.blogspot.com/_G4IFi9T97mU/Snj0a19VRNI/AAAAAAAAEdM/E2bfAXFfoRo/s400/IMG_2397.jpg

(look at the area next to the name. you will see small letters. sometimes, these letters are not printed, but are made of rubber (i guess "cast out of rubber" is the right phrase)

http://3.bp.blogspot.com/_G4IFi9T97mU/Snj0a19VRNI/AAAAAAAAEdM/E2bfAXFfoRo/s400/IMG_2397.jpg

tadlos, October 2009
The cycle shop will be able to tell you - diameter and width are important - often moulded onto the side wall of the tyre when I were a lad... however... You may wish to consider a puncture repair kit and mend the tube with a patch...

http://www.youtube.com/watch?v=ntYIITLp90k

Good luck...

Peccavi, September 2009