I'm a little confused about how companions work. I told Veronica to wait at the 38 and then tried to get another companion to join and they wouldn't. Can I not make companions wait at the 38 and pick and choose who to take? If I tell Veronica that we need to part ways, is she gone forever?

Telling her to 'part ways' just means she'll either go to the Lucky 38 or back to where ever she came from.

You can't have all the companions at once; only one humanoid (human, super mutant, ghoul) and one non-humanoid (ED-E or Rex).

you can't mass all of them in the 38 and pick and choose who you want while the rest wait. And if you tell her to part ways, she just goes back where you got her and you can pick her up from there later whenever you want, as long as you have a decent rep with the BOS

When you choose the option to "Part ways" you can either send them to the Lucky 38 or back to where you find them.

Wow, you guys are quick! Thanks for the quick response.

I think you mean you CAN mass them all in the 38?
Some just take alot longer to get there then others.

Victor even makes the crack that you can invite all your friends and make your suite a "sort of a clubhhouse". I dropped Rex at the 38, when I came back he was gone. I went to see the King, and as I went up to the third floor, Rex goes running by me and out the door and headed for the strip.

Just hire and fire everyone once in the normal way, I did it on my Normal PS3 file before it got FUBAR corrupted beyond all reason.