The "Perfect Hotel," is just what you're looking for. Be it family friendly, all inclusive, or just a place to lay your head. All of these are factors to be considered when choosing your hotel.
I personally love Expedia. In my travels, it has been my go-to website for the best deals on rooms. You also have the opportunity to rack up rewards points, and if you travel often, it's worth it.
Secondly, check reviews over at TripAdvisor. A hotel can be 4 stars, and suck-bad customer service, lack of ammenities, etc. I have stayed everywhere from all inclusive resorts, to a Motel 6. Because I did my research, I have never been disappointed.
So let's start at the top:
What's your budget?
Many sites, including Google, allow you to search by price. Expedia offers a best price guarantee; if you find a lower price within 24 hours, you are compensated.
Have friends or family that work in hospitality? Use their discount! Many hotel chains are moving away from a strictly "family only," policy, extending the discounts to friends as well.
Staying at a hotel that caters more to businesses, may not be a good fit for a family friendly vacation. Many hotels are geared towards the "family friendly" scene, offering pools, play areas, game rooms, or even indoor water parks. And they're not always as pricey as you would think--just do your research!
You'll find hotels that also cater more towards couples or advertise activities for "Girls Weekends," as well, with spa ammenities, and discounts to local attractions such as wineries.
Cities are huge. Use a map app-google maps, mapquest, whatever you want, but make sure your hotel is in the vicinity of the areas you'll be sightseeing in, visiting, etc. Additionally, sometimes (usually), it is cheaper to stay right outside of the city, and many major cities offer great public transportation alternatives (bus lines, trains) if you won't have a rental car.
Also, here is a great opprotunity for me to plug Uber (or Lyft). Download this handy little app on your smartphone (sorry blackberry users, but you can e-mail blackberry, and they'll send you a link...although mine still only works 50% of the time). You can get fare quotes, tip is included, and Uber (so far for me), has been cheaper than an actual taxi!
If a pool is important, make sure your hotel has one. Hotels offer a wide range of services anymore, from spas, fitness centers, pools, casinos, etc. However, some hotels only offer a few of these ammenties. Check these out. Your vacation should be relaxing, and it's not relaxing if you didn't book that hotel with a hot tub to hang out in!
Feel free to include any questions in the comments, or your own expert (or novice!) advice!!