Since you're starting with general questions (what to see, where to stay, etc), you should first get a guidebook or two. I like Rick's Amsterdam And The Netherlands book, but if you can get several different ones out of your library, you'll get more than one perspective.
My big tip for accommodations is that demand outstrips supply, or putting it another way, it's a seller's market. Many of the places to stay are recommended in multiple guidebooks, and since they aren't that large, they book up early. Make reservations as soon as you know your plans, and be prepared to pay more, or get less, then you expected. And don't be surprised to find minimum stay requirements on weekends - year round - since Amsterdam is such a popular weekend getaway (from all over Europe, but particularly for people from the UK - expect to run into a lot of your countrymen!).
Here's a great list of tips for accommodations in Amsterdam from EuroCheapo, which is useful even if you aren't seeking "cheap" places to stay. Pay particular heed to their tip about stairs - they really are that steep. http://www.eurocheapo.com/blog/amsterdam-hotel-advice.html