If you are a young person, of have older teens who have questions about their attending the Lord's Supper, then J.W. Alexander's book "The Young Communicant" may be very helpful.
Alexander, in his usual pastoral way, gives biblical counsel to those who will be going to the table for the first time, or have become new communicants.
Yet it is also good for more seasoned communicants as well. Much time has passed since their first communion, and it is good to be reminded of the first principles of attending. This book is short (54 pages), but is a good place to begin, or begin again, for those looking to the Table of the Lord Jesus Christ.
This is the reproduction of his 1854 book.