Communication - 交通，交流，联系，接触，沟通，交际，打交道
Q1: what sort of things would be connected with 交通?


places are being connected. e.g. "建公路交通兩地" (build highway to connect the two places

Also:

交通(v): back and forth" E.g. "交通來往" (to and fro, back and forth)

交通(n): "traffic" E.g. "香港的交通很繁忙" (H.K's traffic is very busy)


  交流 - to communicate (2 sides don't necessarily know each other)


Also: 交流(v): to exchange (idea, knowledge, information) 


  联系 - 1) n. relationship between things, 2) v. to get in touch with so - Q2: is this after a long time (to get "back" in contact), or just generally?


In general. You can get in touch with people you didn't know before


  接触 - 1) to touch/connect (physical), 2) to contact, to communicate (与/跟) - Q3: what sort of physical action would constitute 接触?


接触 means "make contact; touch" you can use part of your body to 接触 (touch) anything. And two objects physically make contact is also 接触, e.g. 電線接触到水 (electric wire makes contact with water)


  沟通 - to communicate - Q4: what distinguishes the act of communicating through 接触, 沟通, 交流 (and 练习 if 练习 isn't contacting someone after a long time, per above)?


沟: to mix, to circulate 

沟通 : means "to exchange (idea, feeling) ; 


  打交道 - to come into contact with / have dealings with - Q5: what sort of people/things would you have dealings with? Under what circumstances would you say that you have had dealings with so/sth?


people who are not in your circle. We don't say "與父母打交道" or ""與朋友打交道", but we do say "與美國人打交道" , "與某公司高層打交道"