If the top of the tree is still green, does that mean it's ok?

No.  The ability to produce leaves has nothing to do with the structural integrity of the tree.  Inspect the tree for vertical splits, shelf mushrooms, trunk and anchor root decay.  

If the neighbors tree falls on my house are they responsible?

No

Can you cut trees around high power lines?

No.  There is a 10 foot rule.  Anything within 10 feet of a high power line must be cut by a power company or someone with a special line clearance certification.

When is the best time to trim a tree?

Before bud break, or after leaf drop.

How can you tell a pine has been struck by lightning?

You will see a spiral line or vertical crack forming.  When that is evident, the tree will decline rapidly and become hazardous.  It is best to remove them sooner than later, to avoid expensive crane removal.

Do you top trees?

No we don't, and it's against Maryland state law to top trees.

Are landscapers qualified or insured to remove trees?

Tree insurance and workman's compensation for tree removal is completely different than landscaping.  The state of Maryland monitors and enforces qualification and insurance for tree companies.  You must have a tree expert license to operate in Maryland.  Landscapers are allowed to remove trees up to 20 feet.  Make sure whoever you hire has a license and can produce the proper insurance and workman's comp certificates on request.