A great place to buy decorations is at a Party Tree or Party City. From experience, when Halloween rolls around, everyone gets the best decorations from Party Tree and Party City.
There are websites that offer Christmas and Halloween decorations on sale. The website is www.allholidaytreasures.com/. This website has decorations for many holidays.
Kid's halloween decorations can be purchased pretty much anywhere. You can start online at Frontgate or GrandinRoad or can also check out any local retail store around Halloween time.
Halloween and Thanksgiving are often interchangeable. Some of the more generic decorations include the horn-of-plenty, pumpkins and gourds and turkeys.
Halloween clearance products can be purchased from any store that sells Halloween products. The best time to purchase is just after Halloween itself as the stores will be keen to get rid of unsold stock. Such stores include Amazon, Kmart and Target.
Most stores will have Halloween decorations on sale but usually just before and just after Halloween. Stores such as Walmart and Target will offer discounts not tied to sales.
A good place to try trading some of your Christmas decorations for Halloween decorations would be Craigs List. You may also want to consider donating them to a store like Savers. They will give you a store credit that you can then use to purchase Christmas decorations.
You can actually learn how to make very simple, very fashionable Halloween decorations on your own. There are some great sites with recommendations on how to create them like Michaels and Youtube.
Yard decorations can be purchased at any local discount stores like walmart or Target. Dollar stores also often have these decorations but for a better price.
You can buy Thanksgiving decorations at any major retailer such as Stop & Shop, Shaws, HomeGoods, etc. Thanksgiving decorations go on sale a week or so after Halloween.
For your best bargain, I recommend waiting until after the Halloween season. As I have found that holiday decorations are the best and cheapest to buy after the holiday without sacrificing quality.
Special halloween candies can be purchased from candywarehouse.com. Lollipops that have halloween themed designs and decorations are available at the end of summertime through the end of the halloween season.
The best place in which to go for any party supplies would have to be Party City. This store has so much to offer, especially during the time of Halloween. ALso Michael's usually put of a wide range of selections on Halloween decorations for the house.