Have to completely agree with Aviatrix... I'll fly hot & heavy for a bit then not fly for a year or so and the skills do get a tad rusty, but never unsafe.

Taking passengers when I was newly licensed was fun and a whole lot safer than having your flight instructor tell you to "go solo in the practice area and get in a lot of stalls."

In the U.S. you don't require any qualifications to operate the radio, obviously whatever is transmitted is the ultimate responsibility of the pilot in command. Have fun -- I'm sure your friend tell you what to say & will only let you talk to ATC during non-critical phases of the flight. If you screw up it's not a big deal, (s)he will just key down and revise the reply..."Chicago center, this is Cessna 12 alpha...correction it looked more like a yak than a mountain goat."

Just a couple of thoughts about passenger etiquette...1) timfountain makes a good point about keeping your feet off the pedals especially during take off & landing which happens frequently. 2) Ask about stowing stuff if you're in the front seat - I had a friend who hung his camera on the mixture control in mid-flight asked him to remove it. I didn't realize he just put it on the floor but luckily saw it before landing...would not have been happy if it had rolled under one of the aforementioned pedals. 3) If you get even slightly uncomfortable with motion sickness or need to use the bathroom let your friend know immediately. Much easier to be proactive than reactive. 4) While enroute if you see any other aircraft please point it out to your friend even if it is way above/below/going the other direction/etc. The extra set of eyes is always appreciated.