North/West/ towards Mexico City
There's a tollbooth just outside of town. You can get near there, at least from Cholula, by taking a bus to San Martín (about an hour, 10 pesos). Ask the driver to let you off at the highway (autopista or cuota), and you'll get dropped off more or less right at the slip. From there, it should be pretty easy to get a ride to the tollbooth (caseta) where you can then get a ride into Mexico.
Get to the tollbooth at via Atixcayotl. Go pass the caseta and walk about 100m until you see a cool place to hitchhike. Near the spot there's a free WC room. The traffic is going slow, and there's plenty of distance for the drivers to see you and stop. Very good spot.
ATTENTION: It might be difficult to get to Toluca if you're heading from Puebla or Cuernavaca because of low traffic and a lot of villages on your way. Once El Chulito hitchhiked from Puebla in direction of Toluca, and after passing the village of Huitzilac to the MEX106 road he faced a very low traffic density there. This road is cool if you have a plenty of time and enjoy mountains, lakes and lagunas, but it might be difficult to find a place to hitch on some parts of the road because of very narrow paths.
Find your way to the main Puebla bus station, known as La Capu. Plenty of city buses and combis go here for around 6 pesos, or you can walk. From La Capu, invest 6 pesos in a bus to Amozoc, and ask the driver to drop you near the Caseta de Cobro Amozoc. You may need to walk a few hundred metres from where the bus drops you to the caseta. Traffic from here will be heading to Veracruz, Tehuacán, and Oaxaca.