Make money from ads on your website

Make money from website ads - I am very new to this and to be honest i bearly know how to use a computer but i am keen to learn and i was just wondering in your opinion what you think the best type of internet site would be to create the most traffic and what is the best way to approach companies for banners ect. .do you make your own ads spots on the site ,i mean you decide where you want the ads and what ads formats you want to use and then just copy paste a codeline from the ads agengy ,or you have to work from the beginning with an ads agency to create these ads slots ? You may not have intended to make money from your site but now that you have an audience you realise that it's possible, or perhaps you have to start thinking about generating income because your costs to manage the site have increased and it's starting to hurt. You can make chimps change from day one from your 50 hits, but this article is targeted at those that have a larger audience, or perhaps are constructing a business plan (either real or in your head) and would like to know how to go about monetising your website.