With all due respect, don’t believe Lord Ashtar – not that I doubt the veracity of what he says! But his experience has evidently been with “charismatic” parishes – a very small element of the Episcopal Church as a whole.
In my experience, there is usually a point at which the priest addresses the congregation with special reference to welcoming newcomers, explaining anything particular that that parish does in the service. This may not be true everywhere, but I’ve seen a broad sampling of churches over the last 22 years that have done it.
You will find two books in the pew with you, usually a smaller (often red) one and a larger (often deep blue) one. The first is the Prayer Book and the second the Hymnal. I presume I don’t have to explain that the text and music of anything sung is in the second? The Prayer Book gives the standard elements of the various services which are held in Episcopal churches. Odds are very high that you will be attending a Eucharist (communion service); that’s nearly standard for the Sunday morning service these days. It’s on p. 355 and following of the Prayer Book (BCP, for “Book of Common Prayer”) unless they’re a very conservative parish using one of the older formats. The bulletin that you’ll probably be handed when you come in will give you the variable parts of the service and what pages in the BCP the other elements fall on.
The following is the SOP, for your information, on the Eucharist, but does vary from church to church, so don’t expect precise conformity to what I’m listing. But enough of it is either mandatory or almost-universal custom that it’s worth presenting:
As you enter the church building, you’ll be greeted by someone, given a bulletin, and possibly escorted to a pew. When you enter the “nave” – the “auditorium” part of the church proper, there will be people seated or kneeling, and probably organ music. This is supposed to provide time for quiet meditition and self-preparation for the service. Find your way quietly to a seat. Sotto voce conversation at this time is not out of order, but try to avoid disturbing others with it.
The service will begin with a hymn, found in the hymnal, for which you stand. The priest(s) and altar servers, and probably a choir, will come in in procession during it. Find the hymn in the Hymnal, by number (the numbered hymns come after 100 pages or so of service music at the front of the hymnal, designated with “S##” coding.) The priest then formally greets the congregation with one of the responsive exchanges from p.355 of the prayer book, says a short prayer printed there, and a musical item follows. Most of the time this is a setting of the “Gloria in Excelsis,” an old canticle of praise, which will be found in that service music in the front of the hymnal. Some churches substitute another hymn here. The priest then prays the Collect of the Day. You sit down after it.
A reading from the Old Testament follows, usually done by a layman, then a psalm, which is read or chanted, usually while seated. Then there’s a reading from one of the epistles in the New Testament. This is followed by a short “gradual” hymn, for which you stand again. During that hymn, the priest and a server will move into a place in the middle of the congregation, usually a short distance into a central aisle. Stay standing for a reading of a passage from one of the Gospels, introduced with formal sentences. After this you sit again, and the Sermon follows. Most Episcopal priests try to base this on the readings, which are supposed to be on a common theme, and tie it to concerns of the day; it’s usually worth listening to, and not the deadly exegesis of Scripture or hellfire-and-brimstone that sermons are usually reputed to be.
This is followed by recitation by all present of the Nicene Creed, for which one stands. What follows this is the Prayers of the People, normally using one of the formats found at p. 383 ff. of the BCP but adapted to local concerns and usually with time when people offer concerns aloud to ask for the prayers of the other members of the congregation. Note that most forms for the prayers have responses you join in with. At some churches the custom is to stand for these, at others to kneel. This is also the case with the General Confession which follows it. After the priest pronounces an absolution after the confession, he or she usually makes announcements, and then formally wishes “The Peace of the Lord be always with you.” This is a time when you greet whoever is seated near you, shaking hands and if appropriate hugging.
For any and all of this, it’s only good manners to do what everybody else is, but there will be absolutely no problem with your remaining silent on anything you feel inappropriate to join in with. Episcopalians as a rule honor the use of the mind to judge what’s right and wrong to do, and do not expect people to say or do things that are not heartfelt.
What follows the Peace is the Offertory, during which three things are going on simultaneously: the priest and servers are preparing the altar for celebrating the Eucharist, there is music (usually an anthem by the choir, but sometimes a hymn everyone joins in on), and a collection is taken. Your contribution is welcomed but not mandatory.
Stand (or remain standing, if there was a hymn) after the Offertory for the initial part of the Eucharistic Prayer. Almost all of this is said by the priest alone – there is a passage a short way into it where everybody sings the Sanctus (“Holy, holy, holy…Hosanna in the highest”). Immediately following this in some churches, people kneel for the rest of the Eucharistic Prayer (sitting is OK if you prefer); in others, people remain standing for the whole prayer. There is one more response (variable according to which Eucharistic Prayer is used) which everyone joins in on. It’s followed by the Lord’s Prayer and an invitation to communion.
It’s your choice whether to go forward at that time or not – we practice “Open Communion” and nobody is turned away from communion. But partaking of it is a meaningful act to us with implications, so you may not feel it appropriate to do so. There is nothing wrong with remaining in your seat – if you do go forward, and do not wish to receive, fold your arms in an X across your chest and you will not be offered communion – but the priest will probably say a blessing over you. Quiet hymns are being sung by choir and usually congregation as well during the time people are taking communion.
When everyone who wants to has taken communion, there’s a short prayer of thanksgiving, a blessing, a final hymn during which the priest and the rest of the folks in the original procession exit, and a final dismissal.
The working rule is: stand for hymns and the Gospel, stand or kneel for prayers, and sit for instruction (including Scripture readings). We joke about “liturgical calesthenics” to comply with the different times we sit, stand, and kneel.
Nobody is going to feel the slightest antipathy for someone who doesn’t have the routine “down” yet – you may impress Girl Friend’s Mother by simply asking what you’re supposed to do next – it shows a willingness to participate. Yell if you have questions!