You should make sure you have a room large enough for the particular table. It's always best to get a slate tabletop, although this makes the table much heavier.
Before buying a Gazebo you need to know the size you need and whether or not you need any permits or special permissions from your HOA. You need to also consider what you plan to use it for when determining the size.
It's good to know how you plan on using the table. The three major things to look for are the level of the table, the underlay of the table, and the challenge of the table.
The main thing you need to know before buying a lift chair is how much of the cost your insurance company is willing to pay (it's usually part but not all).
You need to know if you need a permit to have one installed, some cities require them. Anything else the pool store will let you know.
Before buying garage doors, you should contact a home contractor and have him or her come out and determine what kind need to be purchased and the value.
Know how much room you will need. Lie can you stretch out in the bed. Is it big enough you will need a CDL to drive it?
You need to know eactly how many gallons and btu that require for your home.
If possible try it out and see if it's comfortable. There are more tips here http://hubpages.com/hub/Futon-Sofa-Beds-What-You-Should-Know-Before-Buying-A-Futon-Sofa-Bed
There is a good guide on what you need to know here www.wisegeek.com/what-are-unlocked-cell-phones.htm
Check out the detailed Sofa Buying Guide that captures the necessary elements to make a great sofa - The Frame, the Foam, and the Fabric
If you are planning on buying foreclosed homes, then you may want to consider buying a foreclosure list. Make sure that the list you are purchasing is up to date and accurate.
Before buying a used Toyota 4x4, you should know the milage, MPG, condition of the engine, when the vehicle was last serviced, and if the truck has ever been in an accident.