Rurik said:
Does that mean that most clan members never meet their husband or wife before marriage and have little to no say in who they will marry? Does the clan leadership decide who marries who?
Some things to remember.
Your mother comes from another clan. She will have brothers in her birth clan and sisters in your clan, but also in other clans in the area. This extended network of kinship provides opportunities not only to travel ('we're off to see Aunt Griselda') that will lead to youngsters meeting, but also to gather recommendations on suitable partners. BTW these inter-clan links are one reason that women are identified as peace weavers, because they have unofficial channels of communication.
Your clan's tula is adjacent to other tulas. Along friendly borders it seems likely that mixing will occur. Such boundaries might include summer grazing or hunting areas where young people could meet.
Clans will gather together at holy days when the tribe wants to increase the magical effect of ceremonies. For Orlanth's High Holy Day you might not go to your temple this year, but to the holy place on the neighbour's tula where Orlanth chllenged the ugly giant because that is the myth you want to do at the ceremony. Holy days are great places to meet others.
I remember reading that in the UK the most likely place to meet your future partner was at a wedding. When you go to cousin Invarth's wedding there will be people there his new wife's clan. One of them may turn out to be someone you will marry.
Thunder Rebels identifies an Ernaldan cult called Vela the Matchmaker. The matchmaker is tasked by the clan to find good matches for its young people. A velan matchmaker will be well-travelled and a good source of knowldege on the nieghbors. Wikipedia has something on the role of matchmakers (http://en.wikipedia.org/wiki/Matchmaking). My own Red Cow material puts the Velan matchmaker on the Women's Circle (http://iancooper.brinkster.net/glorantha/sartar/redcow/redcow.html).
The ring is responsible for negotiating marriages. This should tell you something. Marriage is less about romantic love than economic and political union. This is also a great source for stories. Unrequited love and eloping are all stories in cultures where love is not the reason for marriage but is recognized as a concept.
In addition, note how difficult it will be for someone to marry into a clan that you are hostile too. Even travelling to your intended's tula will be fraught. Such marriages can only occur with the support of your ring and the acquiescence of the opposing clan's ring. This will only tend to happen when the marriage is desirable because it will help end years of feuding.
Hope that helps,