SSL Questions for a new Website

 I am creating a new website I will need to have protected by SSL. I am new to this and have a few questions.
1. Is there any specific way I should design my application, or directory structure for SSL? I will have a "public" and "private"(User must login) section of the website.
2. Do i understand the steps to using SSL correctly? First, purchase a certificate from a company ($45.00 ish?) Next, purchase a static IP from my hosting company, Then have the hosting company apply the SSL to my website?
3. How do you tell an application what pages to secure with SSL and what not to?  What happens if a use tries to access a webpage without using "HTTPS" ?
Thanks for your help.

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