We all know that DiC and Cloverway made some drastic changes in the Anime we have come to know and love. I have wondered for the longest time, 'How did these people come up with the character names? Did they pull them out of a hat?' Hence I "researched" the topic and I have come down to my own conclusion. Remember, there is no concret evidence that these conclusions are true, they are based on what I have learned. Also, I added my own comments to each of the conclusions. I'm sorry if I offended anyone.

DiC Name Changes
Usagi to Serena:
Serena seems to be a shortened version of Serenity, which is probably why in the DiC version she is called Princess Serena.
(Real creative guys!)

Ami to Amy:
Even though Ami and Amy would be pronounced the same in the US, Ami is pronounced differently in Japan. DiC probably changed it to Amy to reduce confusion.
(It did just the opposite)

Rei to Raye:
I have come to the same conclusion for Rei as I did for Amy.
(Once again, confusing the audience)

Makato to Lita:
Ah, yes! The most confusing of all! This one actully makes sense to me now. Lita is actually pronounced the same as the name of one of the moons of Jupiter, Leda. Why they picked Leda out of the 21 moons, I can't be sure, but at least they thought it out a little.
(Wow! I am impressed)

Minako to Mina:
Another no brainer. All DiC did was take away the ko at the end of the Japanese name. The irony of it is that "Mina" is actully Japanese for "everyone" or "everybody."
(Looks like someone wasn't paying attention in Japanese class!)

Chibi Usa to Rini
Rini is a shortened version of Serena, as Usa is to Usagi.
(Better known as the little pink spore...)

Cloverway Name Changes
Michiru to Michelle:
This was expected by most fans, due to the similarity in spelling and form. On the other hand, the names have no where near the same meaning.
(I'm not even going to comment...0_o)

Haruka to Amara:
Amara is still a mystery to me, I still think Alex or Erin or Erika (for short Eric) would have been better. Those names have male/female meanings, but oh well.
(Michelle: "Meet my cousin Amara. I'm in love with her!" Blah!)

Setsuna to Trista:
Um, I have no clue....