Starting to try for Baby #2!!

Oh my I'm sure nervous!! So today is my first day of my period and it normally lasts 5 days so by next weekend we will start trying!! How can I make sure we get pregnant sooner then later?? How can I prepare our son (2 in January) for the baby?? How can I not be so nervous?? I have only told 3 friends that we are going to start trying now everyone else thinks we are going to start trying in September... Ug I'm so nervous about the whole