Can't really say what to do 'first'. There are lots of acts running simultaneously on several stages in several buildings , so you have to have a battle plan as to what to do when. Then fill in between your 'must-sees' by wandering around the midway shops and stumbling onto interesting stuff on the field (sometimes there are pipe bands and SCA battles). If you've never been to the Ag Museum on site, you can check that out too.

Go to the website and print out the schedule for concerts and workshops so you can plan which ones you want to be sure to catch. And print out the map because there can be some hiking between some stages.

fest site

Park near the Sports Museum, hike in to the grounds. Go to the CelticSociety tent, get a program and a t-shirt, talk to some people, and buy some beverage tickets you can exchange for sodas and beers throughout the day.

As I said above, I would not miss Paddy Keenan or The Fuschia Band, and Smithfield Fair is wonderful, and go see Jim Flanagan and Michael Harrison for ballads and Bounds Street for instrumental. As for the rest, there are blurbs in the program to tell you what their stories are. Part of the fun is just stumbling onto something new.

Food, ya never know. It varies, some years it's been pretty shaky. One little truck sells seafood pistolettes, pretty darn good. Other vendors may show up with shishkebab or barbecue or turkey legs or hot dogs. (We don't really go for authentic because who the hell wants hot bangers and boxty when it's 98 degrees out). Fenian's pub last year sold a variety of good foods and desserts made by their chefs, some halfway authentic.   Sometimes there is a table of good baked goods by some little gourmet outfit.   And you can usually buy cold bottles of water (or tuck a few in your backpack) cause it's hot outside (most stages are air-conditioned).