Give people a flavor of all you have to offer on the homepage with links to the specific pages you want people to navigate to. Around 50% of people will land on the homepage, so it is important to help guide people to the things you want them to see.
Horizontal navigation takes up less space on the page and fits more cleanly with modern design but limits the number of menu items allowed. Vertical navigation encroaches on the space but allows for a much larger number of navigation points.
If using horizontal navigation, drop down menus are a very good way to organize the additional pages. Drop down navigation can be just second level navigation or can drop down more than one level.
Breadcrumbs create a trail to let you know where you are in the navigation. These are very effective on larger more complex websites.
Side navigation can also be used on more complex websites to help you navigate around a particular section of the site. Side navigation within subsections is typically used in tandem with horizontal navigation.
A site map lists all of the pages in an outline format. This is effective to help someone look at the breadth of a site. It is also very good to help search engines index a website.
Adding site search into the navigation can help someone find exactly what they are looking for. In some cases it might be a good idea to have curated search that can show up as someone is typing.