Can you offer advice in hosting a party?

I will be hosting a party for the first time tomorrow night, and I’d like some advice.

Here are the details:
– Party is for welcoming the incoming grad students and getting together with everyone before the school year begins
– Will be in my apartment, a 2-bedroom apartment with a very large living room and a screened-in porch
– I am expecting about 25 people
– The people will all be grad students (or partners of grad students) and range in age from 22–32
– Features include a keg, jello shots, Rock Band, and a table for games like beer pong and flip cup
– Smoking will be restricted to the porch
– There are two large sofas, 4 chairs at the table, 2 bar stools at the counter facing toward the kitchen

Main questions:
– What should I do with my cat?
– What should I do for food? (The party is listed on facebook as being from 8pm to 2am.)
– What should I do when the first people get there so they don’t feel awkward for having arrived before everyone else?
– How many additional chairs should I bring into the living room?
– Other general advice for how to keep the party going and make sure everyone is entertained and happy?