How to connect the emitter of a transistor to the base of another transistor? (PNP)
I think what you are looking for is cascoding two transistors as transistors can be CASCADED and CASCODED. that totally depends on the application
 here is a cascade example, as the output of the first transistor connected to the base of the second transistor
"The cascade of a Common Emitter amplifier stage followed by a Common Collector (emitter-follower) amplifier stage can provide a good overall voltage amplifier"



and here is the CASCODE example:



the advantage of using this configuration is to have higher input-output isolation, higher input impedance, higher output impedance, higher gain or higher bandwidth

as I can see from your question, you are dealing with logic gates, or you want to design logic gate. I guess this website is a good start

http://www.allaboutcircuits.com/textbook/digital/chpt-3/cmos-gate-circuitry/