The following is from the Westminster Confession of Faith which most reformed congregations hold to:
Chapter 27: Of the Sacraments
27:1 Sacraments are holy signs and seals of the covenant of grace (Gen_17:7, Gen_17:10; Rom_4:11), immediately instituted by God (Mat_28:19; 1Co_11:23), to represent Christ and His benefits; and to confirm our interest in Him (Gal_3:27; 1Co_10:16; 1Co_11:25, 1Co_11:26); as also, to put a visible difference between those that belong unto the Church, and the rest of the world (Gen_34:14; Exo_12:48; Rom_15:8); and solemnly to engage them to the service of God in Christ, according to His Word (Rom_6:3, Rom_6:4; 1Co_10:16, 1Co_10:21).
27:2 There is, in every sacrament, as spiritual relation, or sacramental union, between the sign and the thing signified: whence it comes to pass, that the names and the effects of the one are attributed to the other (Gen_17:10; Mat_26:27, Mat_26:28; ***_3:5).
27:3 The grace which is exhibited in or by the sacraments rightly used, is not conferred by any power in them: neither doth the efficacy of a sacrament depend upon the piety or intention of him that doth administer it (Rom_2:28, Rom_2:29; 1Pe_3:21): but upon the work of the Spirit (Mat_3:11; 1Co_12:13), and the word of institution, which contains, together with a precept authorizing the use thereof, a promise of benefit to worthy receivers (Mat_26:27, Mat_26:28; Mat_28:19, Mat_28:20).
27:4 There be only two sacraments ordained by Christ our Lord in the Gospel; that is to say, Baptism and the Supper of the Lord: neither of which may be dispensed by any but by a minister of the Word lawfully ordained (Mat_28:19; 1Co_4:1; 1Co_11:20, 1Co_11:23; Heb_5:4).
27:5 The sacraments of the Old Testament, in regard of the spiritual things thereby signified and exhibited, were, for substance, the same with those of the New (1Co_10:1-4).
The following Larger Catechism questions are given out the week before concerning the meaning and proper conduct of Communion.
Larger Catechism Questions
Q. 168. What is the Lords supper?
A. The Lords supper is a sacrament of the New Testament,z
wherein, by giving and receiving bread and wine according to the
appointment of Jesus Christ, His death is shewed forth; and they
that worthily communicate feed on His body and blood, to their
spiritual nourishment and growth in gracea; have their union and
communion with Him confirmed;b testify and renew their
thankfulness,c and engagement to God,d and their mutual love
and fellowship each with other, as members of the same mystical
body.e
z. Luke 22:20. a. Matthew 26:26-28; 1 Corinthians 11:23-26.
b. 1 Corinthians 10:16. c. 1 Corinthians 11:24.
d. 1 Corinthians 10:14-16, 21. e. 1 Corinthians 10:17.
Q. 169. How hath Christ appointed bread and wine to be
given and received in the sacrament of the Lords supper?
A. Christ hath appointed the ministers of His word, in the
administration of this sacrament of the Lords supper, to set apart
the bread and wine from common use, by the word of institution,
thanksgiving, and prayer; to take and break the bread, and to give
both the bread and the wine to the communicants: who are, by
the same appointment, to take and eat the bread, and to drink the
wine, in thankful remembrance that the body of Christ was broken
and given, and His blood shed, for them.f
f. 1 Corinthians 11:23-24; Matthew 26:26-28; Mark 14:22-24;
Luke 22:19-20.
Q. 170. How do they that worthily communicate in the Lords
supper feed upon the body and blood of Christ therein?
A. As the body and blood of Christ are not corporally or
carnally present in, with, or under the bread and wine in the
Lords supper,g and yet are spiritually present to the faith of the
receiver, no less truly and really than the elements themselves
are to their outward senses;h so they that worthily communicate in
the sacrament of the Lords supper, do therein feed upon the
body and blood of Christ, not after a corporal and carnal, but in a
spiritual manner; yet truly and really,i while by faith they receive
and apply unto themselves Christ crucified, and all the benefits of
His death.k
g. Acts 3:21. h. Matthew 26:26, 28.
i. 1 Corinthians 11:24-29. k. 1 Corinthians 10:16.
Q. 171. How are they that receive the sacrament of the Lords
supper to prepare themselves before they come unto it?
A. They that receive the sacrament of the Lords supper are,
before they come, to prepare themselves thereunto, by examining
themselvesl of their being in Christ,m of their sins and wants;n of
the truth and measure of their knowledge,o faith,p repentance;q
love to God and the brethern,r charity to all men,s forgiving those
that have done them wrong;t of their desires after Christ,v and of
their new obedience;w and by renewing the exercise of these
graces,x by serious meditation,y and fervent prayer.z
l. 1 Corinthians 11:28. m. 2 Corinthians 13:5.
n. 1 Corinthians 5:7; Exodus 12:15. o. 1 Corinthians 11:29.
p. 2 Corinthians 13:5; Matthew 26:28. q. Zechariah 12:10; 1
Corinthians 11:31.
r. 1 Corinthians 10:16-17; Acts 2:46-47.
s. 1 Corinthians 5:8; 1 Corinthians 11:18, 20. t. Matthew 5:23-
24.
v. Isaiah 55:1; John 7:37. w. 1 Corinthians 5:7-8.
x. 1 Corinthians 11:25-26, 28; Hebrews 10:21-22, 24; Psalm
26:6.
y. 1 Corinthians 11:24-25. z. 2 Chronicles 30:18-19; Matthew
26:26.
Q. 172. May one who doubteth of his being in Christ, or of his
due preparation, come to the Lords supper?
A. One who doubteth of his being in Christ, or of his due
preparation to the sacrament of the Lords supper, may have true
interest in Christ, though he be not yet assured thereof;a and in
Gods account hath it, if he be duly affected with the
apprehension of the want of it,b and unfeignedly desires to be
found in Christ,c and to depart from iniquityd: in which case
(because promises are made, and this sacrament is appointed,
for the relief even of weak and doubting Christianse) he is to
bewail his unbelief,f and labour to have his doubts resolved;g and,
so doing, he may and ought to come to the Lords supper, that he
may be further strengthened.h
a. Isaiah 1:10; 1 John 5:13; Psalm 88:1-18; Psalm 77:1-4, 7-
10; Jonah 2:4, 7.
b. Isaiah 54:7-10; Matthew 5:3-4; Psalm 31:22; Psalm 73:13,
22-23.
c. Philippians 3:8-9; Psalm 10:17; Psalm 42:1-2, 5, 11.
d. 2 Timothy 2:19; Isaiah 1:10; Psalm 66:18-20.
e. Isaiah 40:11, 29, 31; Matthew 11:28; Matthew 12:20;
Matthew 26:28.
f. Mark 9:24. g. Acts 2:37; Acts 16:30. h. Romans 4:11;
1 Corinthians 11:28.
Q. 173. May any who profess the faith, and desire to come to
the Lords supper, be kept from it?
A. Such as are found to be ignorant or scandalous,
notwithstanding their profession of the faith, and desire to come
to the Lords supper, may and ought to be kept from that
sacrament, by the power which Christ hath left in His church,i until
they receive instruction, and manifest their reformation.k
i. 1 Corinthians 11:27-34; cf. Matthew 7:6,
1 Corinthians 5:1-13, Jude 23, 1 Timothy 5:22.
k. 2 Corinthians 2:7.
Q. 174. What is required of them that receive the sacrament
of the Lords supper in the time of the administration of it?
A. It is required of them that receive the sacrament of the
Lords supper, that, during the time of the administration of it, with
all holy reverence and attention they wait upon God in that
ordinance,l diligently observe the sacramental elements and
actions,m heedfully discern the Lords body,n and affectionately
meditate on His death and sufferings,o and thereby stir up
themselves to a vigorous exercise of their graces;p in judging
themselves,q and sorrowing for sin;r in earnest hungering and
thirsting after Christ,s feeding on Him by faith,t receiving of His
fulness,v trusting in His merits,w rejoicing in His love,x giving
thanks for His grace;y in renewing of their covenant with God,z
and love to all the saints.a
l. Leviticus 10:3; Hebrews 12:28; Psalm 5:7; 1 Corinthians
11:17, 26-27.
m. Exodus 24:8; Matthew 26:28. n. 1 Corinthians 11:29.
o. Luke 22:19. p. 1 Corinthians 11:26; 1 Corinthians 10:3-5,
11, 14.
q. 1 Corinthians 11:31. r. Zechariah 12:10.
s. Revelation 22:17. t. John 6:35. v. John 1:16.
w. Philippians 1:16. x. Psalm 63:4, 5; 2 Chronicles 30:21.
y. Psalm 22:26. z. Jeremiah 1:5; Psalm 1:5. a. Acts 2:42.
Q. 175. What is the duty of Christians, after they have
received the sacrament of the Lords supper?
A. The duty of Christians, after they have received the
sacrament of the Lords supper, is seriously to consider how they
have behaved themselves therein, and with what success;b if they
find quickening and comfort, to bless God for it,c beg the
continuance of it,d watch against relapses,e fulfill their vows,f and
encourage themselves to a frequent attendance on that
ordinanceg: but if they find no present benefit, more exactly to
review their preparation to, and carriage at, the sacrament;h in
both which, if they can approve themselves to God and their own
consciences, they are to wait for the fruit of it in due timei: but, if
they see they have failed in either, they are to be humbled,k and
to attend upon it afterwards with more care and diligence.l
b. Psalm 28:7; Psalm 85:8; 1 Corinthians 11:17, 30-31.
c. 2 Chronicles 30:21-23, 25-26; Acts 2:42, 46-47.
d. Psalm 36:10; Song of Solomon 3:4; 1 Chronicles 29:18.
e. 1 Corinthians 10:3-5, 12. f. Psalm 1:14.
g. 1 Corinthians 11:25-26; Acts 2:42, 46.
h. Song of Solomon 5:1-6; Ecclesiastes 5:1-6.
i. Psalm 123:1-2; Psalm 42:5, 8; Psalm 43:3-5.
k. 2 Chronicles 30:18-19; Isaiah 1:16, 18.
l. 2 Corinthians 7:11; 1 Chronicles 15:12-14.
As can be seen, the congregations that hold to the Westminster Confession of Faith and Larger and Shorter Catechisms take Communion very seriously.
As a Reformed Presbyterian we baptise children if one of the parents is a believer, and usually, only if they have given their testimony before the Session and are church members. Childrens baptism is primarily for the parents and congregation stating, among other things, they will raise the child in the nurture and abmonition of the Lord.
Neither plays a role in salvation. Chapter 3 of the Westminster Confession of Faith, "God's Eternal Decree", goes into this further.
Also Chapter 28: OF BAPTISM, and Chapter 29: OF THE LORDS SUPPER, of the Westminster Confession of Faith gives more explanation.
I hope this is of some help.