I'm going to be attending a two-week summer music program starting a week from today. I'm mainly a clarinet player, but I also do some singing. Anyway, they have auditions at the beginning of the program for some ensembles, and while it's pretty laid back, I still want to do well. Obviously I know how to read music, but sightreading is much different when you have an instrument and are pressing keys to make different pitches. I know that I won't perfect the skill in a week, but in general, what are some techniques that people use? I think I'm most worried about being able to find the starting pitch. I can usually do that when I have accompaniment, but I have no idea what the set up will be like here. Any insight that more experienced singers can add will be helpful!

I learned to sight sing from scratch using Trinity's Sound at Sight (book 1). It didn't take long either.

First of all please don't worry! Many singers are not good sight readers and, unless you have perfect pitch, you probably won't find the starting pitch of a phrase without a pointer from an accompanying instrument or from a given note. You will have a good sence of rhythm and will be able to follow the rises and falls of a melody and that will be a great start. Dig out some of your first clarinet music and an old tutor book and begin working your way through it, singing rather than playing. I think that you will surprise yourself at the results.
Intervals of seconds and thirds should be simple for you. When working out larger ones sing the main notes as normal and then hum the inbetween ones lightly until you reach the next step of the melody. That is as good a way as any to sight sing very quickly.
Enjoy the course and please come back and tell us about it afterwards.

Does that follow the Kódály method?