How will my SS be taxed ?

I will turn 65 later this year. I have not started taking SS yet but want to know how it will be taxed once I do decide to take it.  I live in New York City.  How will the Fed tax my SS once I decide to take it?  Will this income be taxed by New York State as well?  

 

I also have a 403B as well an IRA. Same question for these when I decide to withdraw from them.  

 

Finally, how best to locate and hire a tax expert? I prefer to be able to meet in person or at least talk remotely.  What qualifications to look for to be sure the tax expert is a good one?

 

Many thanks!