Hotels
Most hotels will match the lowest rate you've found online. Additionally, many chains have programs in which they offer big discounts if you find a rate lower than their lowest rate. If their lowest rates aren't as low as the one you found online, ask if they will match the rate you found. Many chains have a Lowest Rate Guarantee program. If you find a rate lower than the lowest one they offer on their website, they will give you an even more deeply discounted rate.
If you are flexible about the specific hotel, bid for a hotel room on Priceline or Hotwire. The hotels are deeply discounted, but you won't know what specific hotel you're staying at until your bid is accepted. There are many strategies you can use to get an exceptionally deep discount.
Always make sure you have read customer reviews, looked at the photographs and checked that the location you are booking is close to where you want to be.
Remember, you can find photos and reviews for hotels on the hotels search results pages. If you need to find out where a hotel is in relation to it's surroundings, click on the MAP or go to Google Maps to check it.
Always retain a copy of this email and any other correspondance you receive as proof of your reservation and payment.
Don't forget your tickets and passports.