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
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.
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).
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.
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.
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.
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
LOOKING FOR ASSEMBLY INSTRUCTIONS FOR THE FUTON I BOUGHT; MODEL FF4157SILS.
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.
Before buying a knife sharpener you need to know if the knives you plan on buying have a warrenty that would include sharpening. Some sharpeners require the use of oil as a lubricant. Make sure this oil is readily avaliable to you.