Hello, Choose the one that have a licence and follow special rules of regulations. I recommend any form the list fx-list.com/brokers-for-us-traders as I have been using their services for a couple of months already and pretty satisfied with customer support and conditions for investments.
I wouldn't say concrete things. In my opinion, you should better search for them on topbrokers.com/forex-webinars There you can read about them and choose those you like. I can't see any obstacles here, this is costless.