Proper etiquette for attending a Bar Mitzvah or a Bat Mitzvah ceremony in a synagogue includes proper attire, and general respect for your surrounding.

Please be sure to dress appropriately, which should consist of casual or formal wear (considerate of hosts' request) that are fashioned modestly. Avoid plunging necklines or short dresses. Men should dress in accordance with host's suggestions, from casual to formal wear, and wear a kippa (a yarmulkah, which will be furnished by the synagogue if necessary). 

Observance of the Sabbath
The observance of the Shabbat laws vary from one conservative synagogue to another, some being more strict, others less so.  In general, driving to synagogue is accepted and parking should not be an issue.  Cell phones should be shut off until you leave the synagogue.  If you are a doctor on call, leave your phone on vibrator, and when called leave the sanctuary and step outside the synagogue to answer your calls.  Like other institutions, smoking is never permitted at a synagogue.

Seating
In general, guests may sit wherever they wish in the synagogue. Most conservative synagogues are "co-ed" and both men and women partake in the various rites and rituals. 

Some seats may be reserved for the bar or  bat mitzvah family. Synagogue members may wish to sit in “their” seat. Respect that. It’s unbecoming and disruptive to hassle (and not worth it). An “oops, excuse me” should be enough to smooth things over.

Arriving and Leaving
People arrive at different times throughout the service. In an ideal world, everyone would arrive a bit before services began, settle in and wait for the rabbi to start. I have yet to see a congregation of idealists. Generally everyone who is going to be there will be at the synagogue before the Torah service. Try to arrive on the early side because some temples have a policy to keep people out during the Torah reading, only opening the doors in between aliyot. During the sermon, the doors might be locked. All these rules are in place to keep disturbances to a minimum.

If you must leave the synagogue during services, do so quietly. Close your siddur, prayer book. Place it on your seat or in the siddur stand by your seat. Some people honor the prayer book by touching the siddur and kissing their hands after closing the cover. Laying a siddur on the floor is considered disrespectful. Try not to leave during the Torah service or during the sermon.

Given the innumerable variables that go into prayer services it’s hard to say how long each service will last. Ask your host.

Movement During Prayer
Bowing is traditional at certain points in the service. A Jewish prayer bow begins with a slight bending of the knees and a little bow from the waist as the legs are straightened. Rocking or swaying helps some people concentrate on their prayers. Souls are likened to flames, and during prayer souls are stirred like flames in a breeze.

Talking During the Service
“If you come to services to talk, where do you go to pray?” One synagogue had this posted on a sign at its entrance. A pointed question for a persistent problem.

It’s a challenge,  but don’t converse during services. Just as you wouldn’t interrupt a conversation with a CEO to answer a telephone call, don’t chat during prayers to God.

Living up to this ideal is difficult because people want to offer their congratulations, greet guests, say “hello.” Try nodding. Wave discreetly. Yes, other people will be talking, but it’s better to do what is right.

What to Say
After services, greet the bar mitzvah boy who read the Torah with the words “Ya-sher ko-ach,” a phrase that means “may your strength increase” and is used as a general way of saying “good job.” Or congratulate a bat or bar mitzvah with “mazal tov,” a general wish meaning “[you should have] good luck.”

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