I used to live in Monterey. It is one of the best places in the world! I would highly recommend a visit to Point Lobos which is just south of Carmel. It's a beautiful wildlife area where you can walk around the point and see many types of ocean life. I would also recommend the Monterey bay aquarium. It is one of the top 5 aquariums in the world.
It's difficult to go wrong eating anywhere in the Monterey/Carmel area but here are a few places I would recommend: dinner restaurant - The Fishwife, the Tap Room at Pebble Beach, Monterey Fish House. Lunch - huge great sandwiches at Compagno's Market and deli, Oaxacan Mexican food at La Tortuga in Seaside, Turtle bay Taqueria is known for fish tacos. Dessert is at Rosine's ridiculous pieces of cake.
If you are a golfer, there are certainly something's you must do. Drive 17 mile drive into Pebble Beach. It's $500 for a round of golf, but it's free to park along the side of hole 17 in the coastal access parking and walk around the famous golf links. Get a few glimpses of the best golf course in the states as you drive through Cypress Point Golf Club. Then for practically nothing play a round of golf at Pacific Grove municipal golf links, commonly called "poor mans Pebble Beach" the front 9 is dull, but the back 9 is on the ocean and it is truly amazing to be able to golf a location like this for $40.
I am not much for the touristy places. I would suggest staying away from anyplace in any city called "fisher mans wharf" or "pier #__". They are almost all tourist traps which are lined with t-shirt shops and "I didn't know it was cold in San Francisco so I will be a San Francisco coat" shops.
However there are some very touristy things we found we enjoyed. Alcatraz in San Francisco is a must see. Book your tickets far in advance. If you can go on the last tour of the day, the sunset tour. They will operate the cell doors and do a few other special things on that tour they don't do throughout the day. While in San Francisco I would highly recommend taking in a Giants game. AT&T park is a great place to take in a ball game, Oco coliseum in Oakland is not (the sewage backs up into the locker rooms and bathrooms a couple times a year). The next 2 suggestions are a little odd and entertainment level can very some based on your tour guide, but we found over time our visitors always rather enjoyed these. The Winchester house in San Jose. Pretty much the heiress of the Winchester fortune went bat sh!t crazy and built the absolute strangest house ever conceived. Plus there is a good collection of old Winchester rifles to check out. The mystery spot in Santa Cruz. It's goofy, you know it's not real, yet it does such a trick on your brain you might just find yourself thinking this was an alien landing site. Plus it only $5. Some people love doing the Hearst castle tour, and I will say the place is incredible. However the day we went it was completely fogged in and we had a terrible tour guide.
There are some very good wines produced in the Carmel valley. If your trip is not going to make it Napa or Sonoma a quick stop at Chateau Julien for a wine tasting is a good idea and not out of the way coming up the coast.
If it's a nice sunny day while you are in the area go take a stroll down Carmel beach. It is the nicest beach not in Southern California.
I will think of some other suggestions for you, I am sure.
All this talk about Monterey, I am thinking I need to plan a vacation and go back!