Prepare to be a bit open-minded about the state of the fortress you take over - there are many different playing styles, and you might take over a fortress, take one look at the work assignments and scream because they're so hideously inefficient, or because some idiot previous player has flooded the fortress with miasma, or dug 15 additional (unsecured) exits as well as your massively fortified main gate or something.
Part of the fun is the chaos in these things, and going along with what's already there - you can try and re-organise the fortress to work in your own style, but that re-organisation and rebuilding will take up most of your year and won't be any fun. Instead, just try and work with what's there, and build your own crazy stuff on top (dismantling existing stuff if necessary). You don't even need to be particularly good at anything - I'm crap at setting up some of the more technical stuff, and yet I've played a couple of succession games and got by without too much trouble (barring an accidental magma flooding, but who hasn't done that in the 3d world?).
Oh, and don't be afraid to write about stuff - I'm probably guilty of going too far the other way and writing far too much (my first year in a succession game was an 18-page marathon, including 3 pages of introduction and 5 more of me looking round the fortress before I unpaused the game, and my last year involved a diary entry almost every other day) but it's great for the other players (and whoever else is reading - hello, CIA!) to be able to keep track of what's happening - how work is getting on on Project X, who's throwing a tantrum, whether their dwarf is super-legendary and capable of frightening off a Titan just by staring at it, or if they've been killed in a freak accident...
Some succession games have rules on what to build or how to run things, usually based around some particular fortress goal, but otherwise the only rule tends to be timekeeping - usually 1 week for a year's play, but even that's not enforced with a rod of iron - sometimes stuff crops up (interrupted by carp!) and you have to drop out or can't complete your turn, but that stuff happens, just pass the latest save along if you have to pull out.