Driving between Siena and Lucca

Looking for advice/recommendations on some towns along the way,

The drive between the two is about 2 hours. You could stop in Prato, Pistoia or Montecatini terme if you wish. You will pass by Florence but don't need to stop there.

donna

Anytime I'm looking for directions from city to city, GoogleMaps.com is where I go.
https://www.google.com/maps/dir/Lucca,+Italy/Province+of+Siena,+Italy/@43.6093516,10.7747401,10z/data=!4m13!4m12!1m5!1m1!1s0x12d57a759d09c91b:0x3082c90e3e48040!2m2!1d10.495053!2d43.8376736!1m5!1m1!1s0x13297c3aca79d275:0x3082c90e3e480a0!2m2!1d11.4339148!2d43.2937732
It's approximately 90 miles between the cities and it takes about 90 minutes.
The easiest way is from Siena through Florence and west and north a little to Lucca.
Don't worry about ZTL's as not every center city has them. It's not difficult to look for the signs indicating ZTL's.
I always rent from either Hertz or through AutoEurope.com--whichever is less expensive. Rental cars should be available in Siena, however most of the towns in Tuscany do not have big name rental agencies.

Are you doing the drive in one day? If so, there will probably be a drop fee for the one-way car rental. There is no drop fee for most 3+ day rentals.

On your way Montecstini Terme and Montecatini Alto are worth a visit and a lunch stop. Near Lucca is Collodi, home of Pinnochio and up the Serchio River is the Devil's Bridge.

In Chianti visit Panzano and stop at the butcher shop (gogle it). Near San Gimignano you will find Certaldo and Monteriggioni, both worth visiting, as well as Volterra.

If you don't visit Volterra while in Siena, it could be a good opportunity to hit it on the way to Lucca. It's one hour longer to go through Volterra, since the road is largely a two lane highway and not a freeway, but you can kill two birds with one stone that way.

Thanks for the responses. I have since gotten a map of Tuscany to really get an idea of where we would be going. But looking at possible routes, wondering about going west towards Volterra and then head north hitting Pisa on our way to Lucca. Any experience with taking this route or would it be an advisable route? Kinda think maybe not taking the major highways up towards Florence and then over to Lucca would be more scenic....

Certainly more scenic. Also you can't go to that area of Tuscany and not visit Volterra, so one way or another, you should drive that route, and you might as well do it on the way to Lucca, since you are going toward that direction.
The Via Volterrana, basically from Colle Val D'Elsa to Volterra, is a two lane highway with curves for sure, then once you come down the hill shortly after Volterra down to the Era Valley, you are on flat valley, so it's not so curvy (but still two lanes).
Be aware that Italian two lane highways are indeed 2 lanes only: each lane 2.5 mts (8ft) wide (if you are lucky) and no paved shoulders on the side. Italians don't like to waste money on more asphalt than they need. So having a narrow compact car, instead of a Hummer, is good, especially when a truck or bus is coming from the opposite direction.

Once you get to Ponsacco, then you get on the FI-PI-LI freeway and head to Pisa, for a short leaning tower visit, and then to Lucca.