"Tips for buying bedroom furniture"

Measure bedroom size including window and door placement. (also measure height from floor of windows)
If trying to match other furniture, bring in a small piece of the item (like a door or drawer, all of which are removable) or also, the original receipt of the piece you are trying to match.
Only pieces labeled as "solid wood" are truly solid. "Real wood" or "all wood" labeled pieces, as well as any piece which is listed as having veneers, can have fiberboard. The more decoration and intricate detail on a piece, the greater chance of the item containing fiberboard and/or resin. (intricate carvings are usually made of resin on lower price range items)
Mattress sizes for beds are as follows: (actual bed size will be larger in both dimensions and varies with construction)

Twin

39 inches wide x 74 inches head to toe

Full

54 inches wide x 74 inches head to toe

Queen

60 inches wide x 80 inches head to toe

King

78 inches wide x 80 inches head to toe
When looking for Full size beds, consider Queen models also. There are only a handfull of beds in Full size. Most beds are available in Queen with Full attachments. The actual bed is the same width Full or Queen, but the Full size is 6" shorter head to toe.