FIrst, you need to find a focus/main keyword
Then you need to insert it in the Google keyword planner to find similar keywords and keyword ideas (you can think of keyword ideas yourself, too.)
You will have 20-30 keyword ideas.
Insert each keyword into Google search
Take note of the LOCAL SITES which show up (Ignore Yelp, etc.. you need to check LOCAL BUSINESSES)
Insert the next keyword and do the same exercise.
If keyword 1 and keyword 2 show similar local site URLs in the top 10, then that means Google will rank both keyword 1 and keyword 2 even when they are on the same page.
Thus, we group keyword 1 and keyword 2.
If keyword 2 did not show results anything similar to keyword 2, it goes to a new group.
You will end up with different target keyword groups.
Each keyword group will be your keywords which you will use for making service pages.