We are still experimenting with techniques of how to choose races.
What we've done the last couple times is the following:
1) Everyone has +1 Political Card
2) All homeplanets are facedown on the table
3) Speaker is chosen randomly
4) Everyone, starting with the speaker, chooses 1 system-tile.
5) Those who are not satisfied with their race, may, again in order, pay 1 Political Card to choose a 2nd system tile.
The player may then choose between the too.
6) This goes on until everyone is either satisfied, or noone has PCs anymore (which cannot happen in 6-8 player games)
Players then have to choose from their hand of systemtiles, without revealing their choices.
Then we decide on the mode of galaxy-setup we want to use, but I guess that's a different topic
Alternatively, we skip the extra PC, and just do two rounds of picking. Three only if we're <=5 players and everyone chose races they already played at least once. Since PCs are equivalent to TradeGoods, we rather use PCs for this, since they have much more fun-potential, and are often burnt in the first two turns for economy-boosts anyway. Which is a little sad after all.
Maybe for a new expansion (*coughcough*) it would be interesting to force more PCs to stay in the game by some means.
We're still in a phase where everyone wants to try out everything at least once, and I guess that phase is rather long anyway with over a dozen races