There are various suggestions at particular points, fuel filter at 75k, coolant at 120k, check and possibly replace timing chain at 100k.
When I buy one I generally replace the standards straight off, oil, filter, air filter, plugs, gearbox oil, brake fluid (and possibly discs/pads at the same time). Then I look a little deeper at things that may need work like the engine mounts, clutch, see if the master or slave cylinder are leaking, look for other leaks too (drive shaft seals from gearbox, main bearing seal etc.)
They are a quite rugged engine but they do have issues, the chassis too. Rust in rear wheel arches, leaks into the rear from rear light seals or boot seals. Possibility of seized rear calipers (generally not the fronts, oddly). Maybe someone put the wrong battery in (since it's reversed compared to common types) and so the terminals are dragged across the top of the battery and sit under the bonnet strut.
If it's had a hard life there's a chance the synchro in second (and maybe 4th, possibly others too) is worn and so shifting can be a bit "notchy".
How would you know it's been well cared-for though? All you can do is make sure you take care of it, and make sure it's in as good a state as you can afford from when you get it.
Enjoy the car though, they're a ridiculous amount of fun and should last a long time if you're careful.