I'm certainly no expert on NYC! But I can share a few things I've learned:
We often stay at the Marquis--it's a good location when we're there for the gift market. As hotels go it's not anything really special decor-wise, but we have always had excellent customer service there. Just be prepared for the surging mass of humanity that is Times Square!
See at least one Broadway show! You're going to be so close to the theaters, you'll be sorry if you don't. (I wish I was going so I could see
Hedda Gabler with Cate Blanchett and Hugo Weaving...

)
Some places we enjoy eating are: Brooklyn Diner (it's not terribly near Times Square but it's a good walk--it's near the Hard Rock cafe as I recall...I love their Strawberry Blonde cheesecake!
Ellen's Stardust Diner is a very 1950s 'themed' restaurant; it's worth a visit. The staff sing and are very entertaining; it's an upbeat and fun place to stop for a meal or a snack. It's pretty wacky and loud, though! Not the place for a quiet meal.
Danny's--on Restaurant Row, they have steak and Thai food. We always eat there, but my advice is to stroll down the Row and pick what looks good.
Ruby Foo's--which is right there near the hotel; very sort of kitschy Asian place, we thought it would be awful but were desperate one evening, and were surprised. We eat there occasionally.
There's an Italian place called Puleo's right around the corner from the Marquis that is actually two restaurants. We prefer the second half right next door, Puleo's Too. Always had great service there.
If you love sewing, I recommend a visit to the garment district for the fabric stores--I've found some great stuff on remnant tables. Some places are 'to the trade' only, but they should have signs stating this.
One place we always visit is the Metropolitan Museum. A wonderful way to spend a day (and the gift shop always seems to have great clearance stuff). If you're into medieval history at all, visit the Met's Cloisters museum (way up at the tip of the island--our cab driver didn't have a clue where it was, but we made it there eventually!) The building is a 12th century cloister moved to NYC. It's just fantastic, the exhibits are beautiful, it's not generally too crowded, and the herb garden is a very peaceful spot to relax.
Really, there's always something going on. If there's a street fair going on in the vicinity, we'll usually grab food there and wander around.
Have a great trip!