Outside of Sigil the next biggest thing you need to learn ‘bout is the Planes. They’re infinite, so’s it’s not like you can learn everything in one shot. But we’ll try our best, hm? Sigil is said to be the center of the multiverse, the center of all. From Sigil one can affect the Planes entire. Or some such drek. Now, since Sigil is the center of things, the going theory is that as a ‘fulcrum point’ (see? You too can learn a thing or two from a Guvner), if one were to nudge Sigil one way or the other in belief, then the rest of the Planes would follow, like a snowball at the top of a mountain making for an avalanche. No one’s gotten a strong enough grip on the city though to test that theory out yet, and I’m rather glad for that myself. Now let’s take a look at why so many cutters believe such bunk.
The planes, such as they are, exist as a representation of a meaning or element or aspect of reality. Confusin’ enough for ya? I’m not yet done. The planes themselves are generally infinite. They exist ‘beside’, ‘between’ or ‘concurrent’ to each other only by our own convention—it is not so simple just to walk around in one plane and mark a point on your map where the other begins - though I’m sure some lucky berk out there will prove me wrong tomorrow. Moving from one plane to another generally only occurs with deliberate intention. Some planes will recognize that you are wishing to traverse to a plane near to it and through either the planes own willingness, or your belief that you’re going the right way after a few days or weeks of travel, you’ll find yourself where you’re trying to get to. I don’t suggest bothering making a map of the journey though, such planes are notorious about making the way unrepeatable.
For other planes, or if you want to get to one without having to traverse the others between, one must hop a portal to elsewhere, have a grand wizard cast a gate or other spell, alternatively one can take one of the many natural pathways from one plane to another such as the river Styx, climbing Yggsdrial, walking the Great Road, or if desperate enough jumping into a astral rift, colorpool, or other open vortex. Portals and spells are usually the safest and most controlled way to travel though, so if you have a choice I’d suggest taking those.
Traveling the Planes: Advice
As we get started on our little tour here, let’s have some advice out front. I’d rather you got home safe and sound to recommend me to your buddies as your personal font of knowledge. From the top:
Plan Ahead: Right cutter, so you're looking to become a planewalker and all you need is a portal to hop through? Well, you could take that approach but it's your neck you'll be risking. Smart cutters plan ahead and research the destination that they're going to as well the places that they plan to travel through. If you have the time and jink, you may even like to consider planning several routes to get to your destination. You never know when your carefully planned route falls apart and you're left stranded somewhere out there on the Great Ring without a gate-key or a clue.
Portal Diaries: Having mentioned others who keep diaries of portals and where they lead to, it's a good habit to get in to keeping this information recorded somewhere yourself. You never know when knowing about a particular portal will come in handy. Even if you can't make use of the portal in a particular situation, that knowledge may be useful to another (since knowledge is power) and it can make a useful bargaining chip.
If you know of a number of portals, it pays to keep some portal keys lying around. It's recommended that you don't carry them around all the time, as this means that if you do happen to pass through them (without intending to use them) then you'll trigger the portal in any case. If you need to use a portal in a hurry and the key takes awhile to get a hold off, keep a spare for emergencies as you'll never know when you need to make a sharp exit.
Travel with Others: The planes can be a dangerous place to travel, that's pretty much common sense and anyone not going out with at least some preparation is simply asking for trouble. There's a fair number of cutters that travel the planes regularly, whether it is transporting goods for trade, passing messages or traveling for other reasons (best not to ask in some instances). Whilst hiring on as a caravan guard on a Prime world may not seem very glamorous, out on the planes it can mean the difference between reaching your destination and not getting there at all.
The plane that you travel on is a pretty big clue on the kind of guide that you're likely to encounter. Having to spend a great deal of time on a particular plane is going to influence a guide no matter what their original character and outlook may have been. For example, it takes a particularly strong individual not to be affected by the apathy of the Gray Waste. If you happen to find a rather cheerful guide on the Gray Waste it's recommended that you be peery in the extreme of their motivation and intentions. Like so much of the advice contained herein - use your common sense, it's one of a planewalker's greatest assets.
Whilst on the subject of Paths, not all roads are ones that you can simply walk down from point to another in order to reach your destination. Some roads, paths, whatever you want to call them have a specific nature that is affected by the choices and actions of those who travel along them. For example, in Elysium if you help a cutter out or perform good actions you'll find your journey goes a lot faster. Fail to help another out or perform a malevolent action and you'll soon find yourself going nowhere. Unfortunately some of the paths in the Lower planes work the same way, except that the choices and actions are reversed.
The planes are a place in flux, molded by belief and infinite in size - the more options that you have for getting from one point to the next the better off you are (in general that is). There's a big debate within the Planewalkers community as to how many routes a cutter should plan when getting around. The favored number is three, although this could just be a nod to the Rule of Three than for any more specific reason.
The main thing to bear in mind is: be adaptable. All the best laid plans can fall apart at the drop of a hat. In fact, should you ever have the misfortune of visiting the demi-plane of hats; you'll soon see how any plan can be dashed asunder. Improvisation, some knowledge and a willingness to go about things in an unorthodox manner are all useful for surviving out on the planes. At this point there should be an inclusion of interesting and pithy quotes from various planewalkers, but budget cuts have prevented any from being included.
What You Know and Who You Know: So you've planned several routes, got the portal keys, arranged for reliable guides and feel ready to head off. Having followed all the advice above it would seem likely that you and your companions reach the destination in one piece. But the one thing that we've not considered so far is the various personalities that you’re likely to encounter along the way.
The planes and places that you'll be traveling through give some hint as to the character of the individuals that you might meet along the way. However, only a leatherhead would presume that all berks in Carceri are treacherous and that all berks on Mount Celestia are paragons of good. Bear in mind that most berks you’ll meet along the way are individuals, which means that they each have their own histories, their own motivations and long-term goals.
Of course I'm not including such creatures as Hordlings and other critters that can't or do not wish to use their sentience for specific purposes and goals. But you can bet your Bigby's Thumb of Hitchhiking that even the tiny Chad on the Plane of Earth can help or hinder a cutter along on their travels. One part open-mindedness, one part peeriness and one part expecting the unexpected is a recipe that the (late) noted scholar and planewalker Rolla Cello put forward in his last treaty entitled 'Rough Guide to Pandemonium'.
So why all this advice on not making assumptions about cutters living on the planes etc. you may ask? Well, sometimes it's not so much what you know as who you know. A word in the right ear can change the fate of kingdoms and more. With so much relying on word of mouth and reputation, a cutter's fortunes can rise or fall with a single word. It pays to keep in the good books of those you cross regularly or are likely to have a run-in with. If you plan to visit Elysium and a Guardinal scholar asks you for an interview before-hand to learn more about a Prime world that you've visited - well, an hour of your time answering questions can go a long way towards getting a friendlier reactions from other Guardinals that you're likely to encounter.