Pisa is a city in Italy.
East towards Firenze
From Pisa there are two roads leading towards Firenze, the A11 and the Superstrada Firenze-Pisa-Livorno. It looks like that most people from Pisa take the latter one, since it is a bit shorter and you dont have to pay toll. An alright spot is southwest of the city on Via Ponte a Viglieri about 100 meters before the intersection where people go on the F-P-L.
There's a small but decent gas station in the suburb of Ospedaletto. Get here by bus number 16, get off at 'Malpighi 2' and walk across the fields. You can continue walking straight until you hit the field, turn right and left immediately into a track. Follow it through the field to a road where you turn left and follow straight until you hit the highway (don't cross it). here you turn left, go under the bridge and through some gardens until you hit the gas station where you need to hop the fence. There might be an easier and more accessible way to get in, but that's the information that is available so far :-)
North towards Genova, France
Take the bus LAM rosso (red line) to the Aurelia bus stop (it's in an opposite direction to the airport so different starting bus stop!). From there go further about 100m until you reach a roundabout and SS1 route. After the roundabout go straight. There is a turn right from the route to the hotel/restaurant where all the cars can easily pull over. Hitchhike there! It took me about 15 min to get a ride to Genova. --Polski Matematyk
Untested: One possibility is the crossing of Viale della Cascine / Via Ponte a Viglieri north-west of the city or a petrol station maybe 1km south of that point.
Accommodation and Sleep
From the tower it is a 10 minute walk out of town where you can try to pitch a tent. A bit South of the train station is a nice area with urban gardens and a big football pitch whose fence's door's lock is broken.
One possible place is here on a meadow behind a parking lot and a car-wash north of the tower. There is a fence which is too high to climb so just walk through the bushes on the left to get there. It is not the nicest place but it is OK for one night and you are back in town in no time to take pictures before the tourist masses arrive :-) To get there walk from the souvenier market west of the tower north on Via Cammeo Carlo Salomone until you see the car wash.
Place still there, camped there as of Aug 2019, dirty place, but fine for the night.
Bus drivers are not concerned by finding out if you have a ticket or not.