Unique visitors instead of total visits — If you're counting every visit in the denominator of the equation, you're including return visits too. This doesn't make sense if someone can only convert once (e.g. signup for an account). Consider how they might check out the site a few times before converting. If so, don't let that deflate your conversion metric. Instead, count the unique number of visitors in any given period. And make your period at least as long as the average time it takes for someone to convert after first visiting your site.
For example, when a customer finds you organically through a Google search for example, that means you have some element of authority. When you have authority, prospects are more likely to enter into your funnel because they know that if they found you relevantly, that whatever it is that you're providing must be of a great value. That's just the nature of SEO and organic search.
Prospecting and marketing are all the things you do to get people into the first of your sales funnel stages. Note that stages are broken into two or more steps wherever possible. A demo could be called a single stage, but in real life it involves a lot of things: contacting the customer, sending reminders, doing the demo, and then following up. Whatever your own sales stages look like, the support you need in managing them will be the same.