Butterflies and Names
Whoever created the analogy of butterflies in your stomach to represent the uncertainties of the first day missed the mark. Recalling my rookie days─now having had a few─the feeling to me is more like buzzards circling in your gut. First day or first shift, take it easy on anything new. This is not the day to try out that new energy drink packed full of vitamins and set-your-hair-on-fire energy elixirs. Stick to what you know works for you; the last thing you need is a worrisome stomach or chemical-induced jitters.
Speaking of sticking to what you know, don't try to be anything but yourself. You are about to learn the culture of the department and "the way it is done around here." I know the academy told you to do things the academy way. However, your FTO and your future supervisors will direct you to the departmental way. You need to change and adapt, because they won't.
When you meet the new staff, remember that they are the incumbents, the veterans; respect them. I had a rookie once who wanted to be the pal of everyone. He wanted to be so friendly and call all by their first names or departmental nicknames. NO. You refer to all by their rank or position. Even the secretaries and staff should be called by titles or Mr. or Mrs. Ignoring this rule, this young man sauntered up to a deputy chief and called him by his first name in front of other staff. The Major, who nearly became apoplectic over this total lack of decorum, then dressed the officer down and sent him packing. Remember this cautionary tale and wait for your seniors to tell you how to refer to them and in what settings.
Learning the Lay of the Land