The primary points of contact for our knowledge of the first century liturgy lie on one end with the Jewish liturgies, and the little data which can be gleaned from the New Testament, and the far later, but well documented, fourth century liturgies. We have a few texts, reliable but vague, from the second and third century that help us piece together the puzzle, but ultimately our study lies in drawing on what we know from these ends, and reconstructing the development in-between.
Three liturgies would have been common place in the first century: the Synaxis, the Eucharist, and the Agape meal. We will look at these each individually but first, a few milestones or key points of interest are important to keep in mind:
The Judeo-Centricity of Early Christianity
1. For about the first 10 years of Christianity, it was almost exclusively composed of Jewish converts.
2. The early Christians were in the habit of attending temple daily. 
3. The early Christians continued celebrating in the Synagogues alongside the Jews on the Sabbath for several years in some places.
4. Up to nineteen years after Christ's resurrection, new converts to Christianity, generally speaking, had to convert to Judaism before becoming Christian. Namely, they were to be circumcised, to eat Kosher, and to follow the Mosaic Law. The Jerusalem Council was called to settle this controversy in 49 AD. 
5. James, the bishop of Jerusalem, while the temple was still standing was in the habit of wearing the priestly robes, entering the temple, and offering intercessory prayer on behalf of his flock. 
The Domesticity of Worship
The Jews allowed Gentiles to participate in their public liturgies at the Synagogue. Gentiles were even allowed to enter the outer courts of the temple.  But there was a rigorous exclusion of Gentile participation in the sacred home liturgies (such as the Seder meal). Initially Christians had no public liturgy, only domestic liturgy and so the controversies regarding the direct inclusion of the Gentile converts into the Christian Church are easily understood within this context. 
The Destruction of the Temple
In 70 AD, the temple was destroyed. This was an earth shattering event for the Jews and a radical shift for the Jewish-Christians. It was a powerful sign that the "Kingdom" had come "with power." 
The book of Hebrews was written in the 60s to explain to the Jewish Christians that Jesus was the true High Priest, that animal sacrifices were no longer necessary, and that Christ's sacrifice was perpetually sufficient.  If it seems obvious to us in hindsight, it wasn't obvious to the early Jewish Christians, particularly while the temple was still standing.
Synaxis is the Greek word meaning "meeting" and is the organic continuity of the Saturday Synagogue worship. Once the Christians were no longer allowed in the synagogues, they continued celebrating approximately the same rite with added Christians developments and themes. The original liturgies would have been held, like the synagogue service, in Hebrew, and some of the words, like "amen" and "hallelujah", survive to this day. In the early part of the 1st century, it is unlikely that the Synaxis would have be recognizably different from the Synagogue service except for the setting. The Synaxis can be understood as the seed of what we now call the Liturgy of the Word. Some key differences include that, in the first century, there were no introduction rites, no penitential rite and no Gloria. These were all later additions.
1. Greeting and Response (The Lord be with you - or Peace be unto you)
2. Lections & Psalmody (The Jews read in order of descending importance, starting with the Pentateuch. The early Christian kept the original order of the Synagogue, but as Christian Scripture became available, it was tacked on the end. Thus the order of importance became reversed for Christians. They read in ascending order of importance):
i. Old Testament Reading
ii. Pslamody (or chanted Psalm)
iii. New Testament Reading (sometimes included non-canonical books like 1 Clement)
v. Gospel Reading
3. Homily (Bishop delivers while seated)
4. Dismissal of Catechumens by Deacon
5. Intercessory Prayers of the Faithful
6. Dismissal of the Faithful
Occasionally a collection would be taken for the poor at the end. This was not the offertory.
Derived from the Seder meal, in its fullest, proper setting, the Eucharist is the celebration of the new Passover. 'Pascha' (or Easter) is the pinnacle of the Christian worship. Initially, it is likely that in some or many Christian Churches, the Eucharist was celebrated but once a year at Passover. The celebration of this high feast of Christian worship expanded to Jewish feast days like Pentecost, and by the end of the first century, the Church had grown to understand every Sunday as a mini-Easter. The Eucharist would have been celebrated early on Sunday morning, a working day in the Roman empire.
The Eucharist was understood as the duty of the bishop and initially, we have every reason to believe that all Eucharists were celebrated by the bishop. But as the Church grew, this became impractical. By the end of the first century, this duty is being delegated to presbyters.
1. Greeting & Response
2. Kiss of Peace
3. Offertory (Communicants bring their own bread & wine to set on the altar)
4. Eucharistic Prayer (The earliest Eucharistic prayer would have been simply a direct continuity of the Jewish eucharistic (thanksgiving) prayer with added Messianic meaning. Noticeable differences in the first century Eucharistic prayer and today's include: a. no Sanctus, b. no Lord's prayer, c. no narrative) The Anaphora of Hippolytus is the oldest Eucharistic prayer we have in tact and it dates around 215 AD. 
6. Communion (Received standing)
There was probably a time where the Agape meal was celebrated along with the Eucharist, as seems to be the case in 1 Corinthians 11. But this practice died out sometime in the first century although the Agape continued by itself for several centuries. The only specific and technical reference to the Agape in the New Testament is found in Jude. 
The Agape has connections with Mediterranean funeral feasts, said in honor of a deceased hero or family member, and with the Jewish chaburah meal. This was a communal meal Jews would eat on the eve of the Sabbath and all important Jewish feasts. Jesus would have had this meal many times with His disciples. It was liturgical, although less formal than the Eucharist or even the Synaxis. Only baptized Christians were allowed to participate in this meal.
Like all early liturgies, it was celebrated in the home. But unlike the Eucharist, it would not be celebrated in the atrium/tablinum but in the dining room (triclinium). Thus, it would be held in smaller numbers and in various homes throughout the Christian community. The Christians traditionally celebrated the Agape on Sunday evenings.
1. Introductory Prayer (the president blesses the food)
2. Meal (In the West, it seems that the breaking of the bread was part of the meal, in the East, it followed the meal. In the West, each person blessed their own cup which would have been consistent with the Jewish tradition at the chaburah meal as opposed to the communal cup for high feasts like the Seder meal.)
3. Washing of Hands
4. Lighting of the Lamp (brought in by the deacon, blessed by the bishop)
6. Bishop blesses the cup (kiddish or kiddush cup, not the cup of blessing which was reserved for the Eucharist only.)
7. Bishop gives thanks for the bread and distributes
Notice the order in contrast to the Eucharist. In the Agape meal, the cup precedes the bread. The Agape is described using the name "eucharist" in the Didache chapter 9. We know this because the cup precedes the bread. Later, in chapter 14, the Eucharist proper is explained. The term Eucharist means "thanksgiving" of course, and in the first century, it was not yet a technical reference to what we now call the Eucharist. Any prayer of thanksgiving at a meal would have been a "eucharistic prayer."
By the end of the first century, the standard Christian liturgical observations would be as follows. On Saturday, you would attend the Synaxis. On Sunday morning you would attend the Eucharist, before dawn. You would go to work that day and then in the evening, you would attend an Agape meal at the house of a presbyter or perhaps the bishop's house.
Mike Aquilina "The Mass of the Early Christians"
Gregory Dix "The Shape of the Liturgy"
- ↑ Acts 2:46
- ↑ Acts 15
- ↑ Recorded by Hegesippus and Preserved by Eusebius in Church History 2.23.4-6 Compare with the requirements for priestly garments in Exodus 28:41-43.
- ↑ Dix, Gregory The Shape of the Liturgy pg16
- ↑ See particularly Galatians 1-2
- ↑ Mark 9:1. Also see Mark 13 & its synoptic parallels.
- ↑ e.g. Hebrews 4:14
- ↑ Hebrews 9:9,23, 10:1, etc...
- ↑ Hebrews 10
- ↑ Thus in the early second century St. Ignatius of Antioch says to the Smyrnaeans, "Let that eucharist alone be considered valid which is celebrated in the presence of the bishop, or of him to whom he shall have entrusted it."
- ↑ See a helpful comparison between Hippolytus and the modern Eucharistic Prayer II here: http://thecrossreference.blogspot.com/2008/02/liturgy-eucharistic-prayer-ii.html
- ↑ Jude 1:12
- ↑ Paul seems to indicate that the "home" is the proper place for this in 1 Corinthians 11:22 (as opposed to the particular home which would likely have been blessed by the bishop as the location for celebrating the Eucharist.) Centuries later, certain canons forbade the use of Church buildings for Agape meals.