All of my favorite radio spots are humorous. Radio is the perfect medium for comedy, which is why so many comedians in the UK get their start on radio shows. Comedy is also a way to make something memorable. So, if you can use humor (probably not a good idea for funeral homes or investment bankers) then you should employ it. On the other side of the coin, avoid sound effects that mimic fire engines, the police, or anything else that makes the radio listener get very confused. People on the road do not need that kind of distraction, so do them a favor and steer clear of those effects.