Beach hop! The beach in downtown Laguna, called Main Beach, is the most obvious spot, but there are hidden beaches everywhere in Laguna. Check out Thousand Steps Beach (between 9th and 10th off PCH), the spots off Cliff Drive or Sleepy Hollow Beach (between Legion and Thalia off PCH) for all the sand you could ever want.
Visit art galleries. Laguna Beach is known as an artsy town. There are art galleries on every corner, it seems (see Resources below). There is truly an art gallery for everyone in Laguna, no matter what style you enjoy.
Pick a fun place to eat lunch and get some ice cream or gelato. Many restaurants are in downtown Laguna, but there are some good spots further south as well, like Olamendi’s for reasonably priced Mexican, Laguna Thai by the Sea (amazing Thai food) and the White House a couple of streets up from Main Beach. Make sure to stop and have some sweets after lunch!
Shop the boutiques. Who doesn’t love to shop? In Laguna, you’ll find lots of boutique stores that are different from stores you’re used to seeing. The clothes can be a bit pricey, so watch out. Walk down Forest Avenue to find lots of shops, or cruise down PCH (Pacific Coast Highway, but the locals always say "PCH"--it's the main drag in town) going south for some of the cutest clothing stores ever. You can also find some unique gift stores on Forest Avenue, too.
Find a dinner place with a view of the water. Laguna is a beach town, so you’ll want to eat dinner at an oceanfront restaurant. Try Las Brisas (killer seafood, but expensive), C’est La Vie (eat outside) or K'Ya on the rooftop of the hotel La Casa del Camino (the view can’t be beat).
Enjoy late night entertainment. For a beach town, there are a good number of places to hang out after hours. Downtown has a couple bars and lounges, mostly down Forest Avenue, and mostly with a cover charge (except Hennessy’s), or you can head south and try Mosun’s Club M to dance the night away. If you’re feeling adventurous, go even farther south and hang out at the Sandpiper Lounge--it’s the weirdest bar you’ll ever go to.