During a 2 week stay in Italy, I spent a few days in Corniglia (and other CT towns). Here are my thoughts on the Corniglia hostel and some restaurants:
Ostello Corniglia (recommended in Italy): I know hostels are not for everyone but I find them a good value for a solo traveler. I actually stayed in a private room which is a 2-bed dorm with an ensuite bathroom. It was less than 40 euro a night - a bargain for the CT. The view is charming with a peek-a-boo slice of the water. The hostel is clean, modern, and comfortable. In their advertising and welcome material they are clear to all they are not a party hostel. I never had an issue with noise or other tourists. As mentioned in Italy, they have strict lock out rules (even if you are overheated and tired from an hour wait (due to a break down) bus at the train station). So, be thoughtful about your arrival time. The staff is helpful and friendly! I would definitley stay there again.
La Posada (recommended in Italy): Corniglia Via alla Stazione, 11 - just past the stairs; This was a dream dinner. While sitting in a lovely garden I enjoyed a beautiful sunset over the water! The views are only surpassed by the food. Started with a glass of delicious prosecco while enjoying the view and looking at the menu. Ended up ordering a pasta with pesto and for secondi a potato and fish dish. Everything was wonderful. The staff is friendly, fun, and welcoming. Christian (the owner, I think) is an energetic guy who makes you feel like a regular! He cracked jokes the whole time and ran from table to table!
Caffe Matteo is run by Christian's friend Ricca. A great place for breakfast or an afternoon caffe! The main entrance is on the main street (Via Fieschi, 157) but it also opens out onto the main piazza which is tree and umbrella covered. Excellent cappucino and pastries.
Il Pirata (Vernazza, Via Gavino 36 - by the post office): This place is also recommended in Italy. This restaurant is not on the main street of Vernazza but RS gives good directions or ask local directions to the post office. While it doesn't have any views, it doesn't lack any charm either. Stopped one day for an afternoon treat (limoncello gelato) and came back the same evening for dinner! I made reservations with one of the owners and was welcomed by name at dinner! The owners are brothers and keep up a running conversation with all the guests as do their other staff. The service was outstanding! The waitstaff suggested risotto with seafood (clams, mussels, and shrimp) and panacotta for il dolce - both were excellent!
Shopping - The Path Shop (Vernazza, Via Caattino, 5) This tiny jewelry shop might be fairly new. Look for the sign on the main street (on the left if walking toward the harbor.) You will climb up a few steep steps and see the entrance on your left. A little tricky to reach but well worth it! This shop is unlike the more touristy (but still good) shops on the main street. The owner packed the place with lovely jewlery that is reasonably priced. I bought a gorgeous green glass bracelet.