Use ContourLabels
ContourPlot[Sin[x] Sin[y],
{x, 0, 3}, {y, 0, 3},
Contours -> {.25, .75},
ContourLabels -> (Text[#3, {#1, #2},
Background -> White] &),
ContourShading -> None]
ListContourPlot[
Table[Sin[x] Sin[y],
{x, 0, 3, 0.1}, {y, 0, 3, 0.1}],
Contours -> {.25, .75},
ContourLabels -> (Text[#3, {#1, #2},
Background -> White] &),
ContourShading -> None]
Bob Hanlon