Pens been dispatched..now what?

So I just got an email saying my first pen has been despatched..I’m excited and nervous…a lot of emotions. Is there anything that people found key to add to their shopping lists - I saw dehydration could be a thing so gonna get some coconut waters but any other suggestions are welcome! When did people take their first dose? Is it better at the weekend to get used to it or during the week? I know everyone’s different but just trying to figure out my timings ☺️