I always though seekings as an improvement of the character. The Avatar will put the character to the test, and if he is worthy, his knowledge of reality will improve.
This is kind of the header for all the ideas and seekings I have narrated in the past.
I'd like to start with the five W:
The focal point being that the character and his Avatar will interact, with not much other things happening. His Avatar will take different shapes in a seeking, and the character may know, or may not know that it is his own Avatar in a different shape.
This is by far the most difficult question to answer, what is going to happen? I prefer to talk to the player, what are their expectations? I usually also want to add to the seeking any conflicts that the character may be undergoing right now. Has he recently fled a battle cowardly while his own cabal fought for survival? Has he killed someone in cold blood? Has he lost someone important to him and needs to let go? The centre of attention, the big lights, should be in the character, in his development, in how he uses his powers on relation to the rest of the world. Is the character happy with his current state? I usually mix all this into a little story where the character will face his errors, his desires, and his phobias, all on the hands of his Avatar.
Most of the time, I prefer a battle in the centre of the mind, when all is done, there has been no time lapse, the character changes internally, nothing appears to be different on the outside. But sometimes, the character will want to take some time alone, or somewhere (more of this below), time to prepare his mind for what he is feeling is going to come. Or maybe his Avatar is furious and will abduct him for some time while they clash in a challenge.
As stated above, I like to take the seekings to imaginary landscapes, even if it appears to be normal day-to-day reality. Technically, the Avatar will create an Astral Realm where they will interact, can other people see this if they are in the right moment in the right place? Technically yes, but I prefer that that does not happen, that will shift the focus out of the character, but it can be a powerful tool in the future, if for some reason the character ends up there again while not in a seeking.
Sometimes the character needs to go to some place, like a real place, that will take time, maybe it is the travel that matters, not the destination. But always, always, the places need to be important for the character. With symbols, colours, forms, all making patterns that are important to the character.
This is also a very difficult question. Some answer that the Avatar doesn't really want the character to succeed, because understanding the reality is a here and now thing, and Ascension is all about the there and after. Of course Avatars don't seem to simply give you a strait answer (that will simply be bad for the story), so who knows really? Sometimes the character will challenge his Avatar (I AM prepared, lets put this to the test!), sometimes the Avatar will appear and force the character to the test, other times it will be an arrangement. The important part is to remember that the Awaken are creatures of change, they are in constant process of learning, becoming more than they were, learning, living. An epiphany awaits at the end of this road, with new understandings on how the universe really works.
Over the years, I end up not using most of the rules for seekings (AKA not throwing ANY dice, all should be made by the choices of the character). It is just me and the player. And it is true, that sometimes we players, simply do not have the time to do this. My solution ended up throwing away all real time interpretation, and focusing on writing something with the player (via email, usually). It is not a one sided work, we are both involved and we have a clear set of things we want to see happen in this seeking.
As how they can fail, I usually don´t make the characters fail if the player doesn't want to, although if the character doesn't have some depth, some inner conflicts that can be solved, some goals we needs to accomplish, then it is possible that I will tell the player that it is not the moment for a seeking, that the character is not prepared. If they still are going for it (mule headed charging forward) then maybe they will fail (in this case, I usually default to the interpretation and a story ready for the character to challenge), if they succeed, great, I was wrong (we can all be wrong), but if not, they will fail.
As for the experience, I really don´t like them to loose it, for two reasons, loosing experience sucks in too many levels, it is a really un-fun thing with no real mechanic to pass directly through the story. I prefer to make the loose a permanent point of will power (they can buy it back with the experience anyway, but it has a meaning in the story), but I will not do so if the players really wants his character to fail. And second because it is a lot of it. It is the second most expensive thing in all world of darkness (apart from stupidly high cost disciplines for ghouls (levelx25 and the such)), loosing a lot of any thing is something players don´t want to see.
I also state that the experience used on a failed seeking cannot be used again for the purpose of adding Areté. They can spends it in spheres, abilities and all that. But they need to start from ground zero for they new seeking.
And of course, I tell them all this before they start a seeking. Mage, over all rpgs, is a game that the players have more control of. Our goal should be to tell a really good story and seekings provide a one-to-one which can really add to the depth of the characters. We should use it as a tool to improve the story, as characters use it as a tool to improve themselves.
By involving the player in the story of the seeking, the player founds out how really hard is sometimes to come up with a story for a seeking, and players really want things to happen, most of the time, I have found out that they are the persons who most viciously will treat their own characters. They will put them in the light, they will measure them against all odds, just to see them come victorious on the other side.
Finally, one of the most fun seekings I have narrated, come up when one hermetic player wanted to do the same theme for all the seekings. Whenever we decided that the character was ready for a seeking, it will disappear and reappear in a magical solomonic labyrinth (not a nephandic one, mind you, just our typical multi-chose place). With new tests, new traps, new everything, but the same place, the same temple. Over the time, the character came to like the place, it was like an old enemy you have fought many times. It became a nostalgic place for him. And of course he was shocked when the cabal discovered the place in one of their Umbra-exploring stories.