First contact: Who should represent humanity?

There are a few hurdles, the least not being their existance being proven. Potentially all those who are under the impression they have had an experience of extra-terrestrials may already have made contact. Additionally, all those who had any extral-terrestrial experiences and chalked it off as probably dreams, coincidences or something that could be otherwise explainable (such as myself) may already have made contact too.

"Firstly, we need someone to initiate communications, and for that we need someone who is friendly, cultured, well spoken, and can maintain an immaculate appearance."

In regards to your requirements, friendly is probably a benefit, but this too is an assumption. The key is in the next word. Cultured. We could speculate about extra terrestrial culture, which would most likely range a great deal. However, just as this world has a wide range of cultures and their origins and purpose can often be deduced, any other culture is likely to differ from the cultures here. As such, the values a "cultured" person may possess here may conflict a great deal with those of another. Furthermore, someone who held the view that they were particularly cultured already has connotations of someone who is self absorbed and believes themself to be superior. Surely that notion itself is a recipe for immediate conflict or disdain. Going back to friendly, this has cultural implications too. You would hope that any widespread race, with experience of studying other species would be possessed of logic and reasoning. Their own society might still embrace certain behavioural traits, but their expected reaction from another species may be shaped by their initial studies.

Being well spoken may too be immaterial - this would depend on how communication took place. If we were to believe some reports of non-verbal communication, being well spoken may be immaterial. Indeed, having a somewhat cluttered mind might add character and improve relations. For the records, the non-verbal component is highly logical and one I would expect. Vocally, there are a wide number of differences even in species. Physically however, there are commonalities in nerve structure and brain plasticity. Your brains can adapt to a wide range of inputs, and devices can be readily accepted for new sensory enhancements. Mainstream and publicly tested devices range from simple visual devices, such as via the "Brainport" project (input(, to hearing devices (input), simple scans for computer game control (output) and more. Your brain does not require "words" for thought. Language is simply a programmtic layer which can be bypassed.

In regards to immaculate appearance, one view of immaculate may not conform to anothers. This is shaped by society, species difference, and more often ease and competition. The less threatening, slightly scruffy and more relaxed individual may often be interpreted as being more welcoming and receptive than the very smart, immaculate, rigid and formal individual who may be seen as competitive or hostile by comparison.

In terms of human society, who then is the "best bet" for contact? Based on the individuals in this world, I would say the best bet(s) are individuals, speaking not for authority but for themselves. Not just one, but many, each providing a distinct perspective, and in a few lucky cases a comprehension of all cross sections and the nature of the species.

originally posted by: undo
a representative selection of the mammal species that have unique communication skills,perhaps:

a dolphin that has learned to communicate thru computer interface. to represent mammal life in the sea.
a gorilla that has learned to communicate thru symbols (sign language). to represent mammal life on the land.
and finally, a human who is multilingual and has a good concept of metaphor, symbol, and can think out of the box. to represent mammal life that has learned how to exist in the sea, land and air.

Dolphins and whales being some of the most welcoming empathic and playful species on the planet - certainly a good start
I don't think you'll need multilingual, but we'll see eh. Same applies to metaphor and symbol - take away the language layer and your brain tends to work in that manner regardless.