I'm going to leave it to the men of GC to make suggestions regarding how to behave on the first night but I do have two tips.
1) Absolutely make sure that you are true to the chapter's personality. If your members are not the type that would act "really enthusiastically" don't ask them too. PNMs can smell "fake" a mile away and they don't want to pledge a fake chapter.
2) If at all possible before rush starts, or even during the year to brush up for next year, invite a sorority to practice a mock rush with you. I don't think men practice talking to walls like we do; so get some live bodies in front of the guys. You can use a mock rush party as an ice breaker for a real party with a sorority.
