Countdown

Firstly, my intention here is NOT to just publicise my business but learn from  and hopefully help other new starters with the process of launching an online business, so I wont be pushing my website address every two minutes!
Wow... never been so excited and scared in my life. Complete the purchase of my online business on 19th of September, then ...its down to me. Websites have been created and lauched, but not advertised . My head is exploding with ideas on how to advertise, where to advertise, SEO PPC... OMG! ANY advice on how to start marketing my websites greatly appreciated. Seems very daunting at the moment, so much to learn. Which SEO companies do you rate? how much success have you had with PPC? any tips? any other top ideas on how to advertise?