I love duos, I started out this way, being mentored (yes exceptionally lucky) and introduced to other ladies clients before going solo.
You absolutely have to respect a code of conduct in my opinion, for example not give out your number to the client without asking who's booking it is first, even then I'd be very reluctant. Give priority to her as a 'hostess' almost introducing you as 'the new girl' to play with, using it as role play at times. Its endless the fun you can have with another girl to plot scenarios and team up to create fantasies. BUT I have to genuinely get on with my duo girl to turn that ordinary booking into a memorable one.
Otherwise I'd rather go solo.
I always meet prospective duo partners first for coffee, its essential for my clients that I can confidently reccomend them. To be groomed or dressed a certain way or act how they would like, its like interviewing each other - same thing - its a job. Its another area where your intuition is needed.
Like in any business arrangement, choose your partners to suit the needs of your client and booking. Do they like two girls of similar build, bust, colouring and demeanour or do they want a contrast. Its intuitive.
I am in the mature bracket so I think age does help suss out potential trouble makers easier. Take nothing personaly and my policy is one strike of bad behaviour and they are out...no more duos with me, there is no space for games or drama. That wouldn't suit my clientelle and reflect badly on me.
As I am now semi retired and only see longstanding regulars, its more important than ever.
Find and meet a few good girls you can work with, help each other out, trust a little, be kind but don't trust too much with anything irretrievable physically or emotionally. Its worked brilliantly for me, and has been invaluable.