In Michigan, there is a service called Miss Dig for identifying buried utility lines. We've just moved from Michigan to New Hampshire, and we would like to know where our utility lines are buried. What service should I call?
811 is the universal number for all US states.
Canada has different numbers.
A list of "Know Before You Dig" services, by state, is available here: 811 Website
For New Hampshire, contact Dig Safe Systems, Inc.
This question is really too localised, so this answer doesn't apply to all, but in Australia there's Dial Before You Dig on