Yes, minterms are 1 and maxterms are 0.
As far as I'm concerned, the K-map is mainly used to find the sum of minterms.
Just looking at the 1's in the chart, you can see that the original equation looked something like this:
f(x) = a'b'c'd' + a'bc'd' + ab'c'd' + ab'cd + abcd' + ab'cd' + a'bcd' + a'b'cd'
However, you can circle the ones to create a sum om minterms. Like berkeman said, you want to group the terms into the largest clumps you can. I've redrawn the K-map with colours for clarity:
-red: a'd'
-orange: b'd'
-blue: cd'
-green: ab'c
Inside each circled area, look for the values that do not change. For the red one, the circle covers 00 and 01 horizontally. The first digit represents the a, and because it is a 0 and not a 1, you get a'. Vertically, the red circle covers 00 and 10. The 2nd digit remains the same this time, and this one corresponds to d. As a result, you get d'. Finally, you put the a' and d' together to get a'd'.
Do that for the rest of the circled clumps and you should get the answers I listed above (unless I've made a mistake).
Your sum of minterms will be:
a'd' + b'd' + cd' + ab'c
Note the circles can only be of size 2^n (size 1, 2, 4, 8, 16).
