We spent a week in New York last year.It wasn't my choice to go,but i have to say it was fantastic.We went to Central Park during the day time,but i never felt threatened at any time during my stay.As for tipping,i tipped 10% in restuarants,even if the tip expected was added at the bottom of the bill.I tipped the full amount for breakfast as it was only 2 or 3 dollars.1 dollar a drink in bars if i was having more than 1 round of drinks.Nobody ever complained about the tips i left.Go on the Staten island ferry to see the Statue of liberty.It is free and goes straight past the Statue,don't waste time going onto Liberty island.You can buy a hop on hop off bus ticket,well worth it if you're there for a short stay.Go to the top of the Rockerfeller building rather than the Empire state.It is the best place to see the empire state.If they have time,go up at day and night time.Tell your daughters boyfriend to go and watch some sport if possible.I went to an Ice Hockey game at Madison Square Garden,great experience.Next time i go i will go and watch the Yankees.Whatever they do they will have a great time,i did.

You should tip at least 15% in restaurants unless the service isn't up to standard. Tipping only 10% implies the service was sub-standard.

Its worth looking at the walking tours. I went on on Food tour of Greenwich Village which was great. We saw things we wouldn't and sampled food in lots of places. It lasted 4 hours but was well worth it and cost around $44 pp. It needs to be booked before you go as they sell out. To get the most out of it she will need to plan it. There is really more do's than dont's. Visitors at Macy's can get 10% off if they take id in and register at the customer service desk. NY has changed a lot over the years and is safer now than used to be. The subways are good to use just do a little research before you go. She will love it.

When in restaurants ask for the set menus they never just give you them...can save a lot of cash.
the rockerfella is better to go up just before sunset as you will get great pictures both day, dusk and dark of the city. Book a hotel near times square towards 5th ave as we stayed there and it is a great location to get around...if you havent booked hotel have a look at the salisbury hotel and the wellington hotel...great location for both.
Enjoy
Liz