Who is entitled to partake in the Lord's Supper? 1 Cor 11:27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.


What does this mean, "unworthily"? (cp. 1 Cor. 11:29)

Religious denomination practices range from churches where only the leaders are entitled to take communion whereas other churches encourage communion even for those who didn't prepare for it. 

So how can we make sure that we don't approach communion "unworthily"?
John Gills exposition of the Bible always explained it the best for me:


  The bread and cup are called the bread and cup of the Lord; these may
  be eaten and drank "unworthily", when they are eaten and drank by
  unworthy persons, in an unworthy manner, and to unworthy ends and
  purposes. The Lord's supper may be taken unworthily, when it is
  partook of by unworthy persons. 
  
  This sense is confirmed by the Syriac version, which renders it ולא
  שוא לה, "and is not fit for it", or is unworthy of it, and so the
  Ethiopic version; now such are all unregenerate persons, for they have
  no spiritual life in them, and therefore cannot eat and drink in a
  spiritual sense; they have no spiritual light, and therefore cannot
  discern the Lord's body; they have no spiritual taste and relish, no
  spiritual hungerings and thirstings, nor any spiritual appetite, and
  can receive no spiritual nourishment, or have any spiritual communion
  with Christ: and so are all such persons, who, though they may profess
  to be penitent ones, and believers in Christ, and to have knowledge of
  him, and love to him; and yet they have not true repentance, neither
  do they bring forth fruits meet for it, and so as they are improper
  subjects of baptism, they are unworthy of the Lord's table; nor have
  they faith in Christ, at least only an historical one, and so cannot
  by faith eat the flesh, and drink "