Our bed pillow options are changing dramatically as sleep technology advances.  Choosing the best pillow is not something I can do for you.  I can give you information that will assist you in your purchasing:

Size:

The size you choose for your bed mostly depends on your mattress.  King size sheets come with extra long pillow cases that would be best when used with King size Pillows.  Standard and Queen size pillows normally only differ by a few inches and either size is fine for any mattress up to queen size.  King size pillows can be too long and unyielding to a person, so you might be better off with 3 Standard or Queen size pillows on a King size Bed.  Pillow cases can always be purchased separately to make sure you have 3 cases that match your sheets.

Sleep Position:

The position you normally find yourself sleeping in is a major deciding factor when purchasing new pillows.  Back sleepers would normally be better suited to thinner less supportive pillows to obtain proper spinal support.  Side sleepers could use the extra support of a medium firm or contoured pillow.  Stomach sleepers need to be extra careful to get thin pillows to avoid suffocation from their pillow.

Pillow Filling:

If you prefer a very thin pillow, Down or Synthetic Down should work very well for you.  If you prefer a supportive pillow, Memory Foam or Latex should suit you.  Memory Foam will react to the heat and weight of your head and conform around you giving outstanding support.  Latex relieves pressure a little better than memory foam and bounces back immediately if you move in your sleep.  Memory Foam can take as long as 30 to 60 seconds to go back to its normal size, which may wake you if you move a lot. 

Pillow Firmness:

If you prefer a thin pillow, a down pillow should work well for you.  Make sure you purchase a pillow that gives easily and is not overfilled.  Memory Foam pillows come in many different shapes and sizes.  In a contoured pillow, 3 lb. memory foam seems to work best.  A higher density of memory foam is normally used in a comfort pillow (normal shape) and it is still pretty soft.  A latex pillow is normally very supportive and bounces back right away.

Pillow Covers:

Many different kinds of fabric are used to be the outer shell of a pillow.  Memory Foam Pillows use a terry or velour cover that can be unzipped.  These pillows do not require a pillow case and will honestly work better without one.  Latex, down, and feather pillows should be covered with a pillow case to avoid stains and keep your pillow in the best condition possible.  Make sure you keep the manufacturer's cleaning instructions in case your pillow gets dirty.

The Bottom Line:

The Bottom Line is that you know what you like.  The information contained here should help steer you toward the best pillow for you.  Don't forget that we spend a third of our lives in bed and deserve to be comfortable.  Choosing the right pillow can help with that.