Creating concentric circles in Illustrator is super simple. You can create a circle and simply use Object Path>Offset Path to create a new one and specify the distance between the circles (for smaller, minus then the integer) than the original circle or larger. This method lets you create each circle one by one. If you want to create a bunch of them, go to Tools and select the Polar Grid Tool (it’s under the drop-down from the line segment tool). Double click to bring up the Polar Grid options and set the Concentric Dividers to the number of circles you want and take the Radial dividers down to zero. Hold down Shift as you draw to constrain them to perfect circles. If you want to use the circles as pathways for text, Ctl-A to select all and Ctl-C to copy (you’ll see why in a moment).
To change the stroke size, colour, etc, you need to Ungroup them (Shift+Ctrl+G). To chop the circles up a bit, use the Pen Add Anchor Point and click on the circles to create extra nodes; select nodes with the Direct Selection tool to cut the node using the Anchor Cut Scissor tool from the Properties Palette. Cut a node further along and Delete to get rid of bits of your circles and leave other bits of circle segments. Change the colour, size, segment end style, etc using the Stroke options on the Properties Palette.
To add text so that it continues from the circle segments, lock your concentric segments layer, create a new layer then use the command Ctl-F to paste the circles, previously copied, in place. Under the Text tool, select the option Type on Path and type your text. Make use of the Add Nodes to cut the text path segment just after the coloured segment lines. You can also select with the Selection Tool (V) and drag the text path handles to shunt the text along.
The Polar Grid option is worth knowing about if you need to create a number of equi-distant circles quickly. And, it’s nice and easy.