Whenever I go on vacation. I do a lot of research and price comparison before I book anything. Most of the time I usually put together my own trips instead of buying vacation packages from sites like Expedia or Travelocity.
1) Select your travel dates asap
2) Once you know your travel dates observe the flight, hotel, and car prices for your dates. That way you will know what is a good deal when it comes around.
3) If you find a vacation package you like try and build the exact same package individually. Compare the prices you might save some money.
4) Always look for promo codes and coupons.
These are my favorite sites I like to use when building a vacation.
http://kayak.com - This is a great site that will do a lot of work for you. It will search Travelocity, Expedia, Orbitz and others all at once and give you a price to compare. You can search vacation packages, flights, hotels, cars and more. I normally use this site to get an idea of what the current rates are for my trip. You can also sign up for email alerts. I sign up for daily email alerts on my flight dates. Kayak.com send you an email alert with a graph of your desired flight price from the day you start. So you can watch when prices dip or skyrocket.
http://Airfarewatchdog.com - This is a good site for flights. It will provide promo codes if there are any for flights. You can also sign up for email alerts on this site too.
http://slickdeals.net - This site provides printable coupons and online promotion codes. It also has a forum where people share information on good deals for practically anything. I like to venture here when I'm looking for promotion codes for sites. You will be surprised at how much you can find. I usually go to the forums and do a search for whatever I need.
http://retailmenot.com - Have you ever done some online shopping and when your checking out you see a box for promo code? Well if you go to this site you can enter the URL and it will list the promo code(s) for the site if there are any.