Jason Cawley
Wolfram Science Group
Phoenix, AZ USA
Registered: Aug 2003
Posts: 712 
In general, for Mathematica help the places to look are first the help browser, then the Mathematica book, and then online resources like the Information Center 
http://library.wolfram.com/infocenter
If you still can't find what you need you can try the MathGroup discussion list, where you can submit a question if there is no relevant thread already 
http://forums.wolfram.com/mathgroup/
This forum is specifically for New Kind of Science subjects, rather than general Mathematica ones.
All that said, to address your actual question, you can probably get what you want with just the optional argument ContourLabels>Automatic. For example 
ContourPlot[x Sin[2 Pi y], {x, 4, 4}, {y, 1, 1}, PlotRange > {4, 4}, PlotPoints > 25, ContourShading > False, Contours > 7, ContourLabels > Automatic]
Notice, the Contours argument tells it how many lines to draw. If you just give an integer, it draws that many lines, and they are evenly spaced within the specified PlotRange. ContourLabels tells it to label each line with the Z value of that contour.
You can also give a list of z values instead of a integer number of lines, as a value for Contours. E.g.
ContourPlot[x Sin[2 Pi y], {x, 4, 4}, {y, 1, 1}, PlotRange > {4, 4}, PlotPoints > 25, ContourShading > False, Contours > {3,0,2}, ContourLabels > Automatic]
That draws only the z = 3, the z = 0, and the z = 2 contours  and labels them.
Notice I also used the PlotPoints argument. With the default number of points, some of the contour lines might look a bit squared off in places. Increasing the number of plot points gives a smoother shape  at some sacrifice in rendering speed.
Incidentally, if you want to see a 3D graphic version of the same, you would use something like 
Plot3D[x Sin[2 Pi y], {x, 5, 5}, {y, 2, 2}, Mesh > False, PlotPoints > 50]
I hope this helps.
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