What advice would you give for massaging someone who is suffering from a trapped nerve?

As Nigel stated, it depends on where the pain is eminating from, as to whether he case needs referring. A lot of trapped nerves are caused by inflammation in the muscle fibres. This means the most effective initial treatment would be to perform lymphatic drainage routines to help stretch & relax the tissues allowing for lymph to be drained. Origin & insertion work will then allow the muscle to release any other toxins so as to regain normal function, This can be done by either static trigger point pressure or deep tissue work. Hope this helps & the issue recovers soon.

On the information I can gleam from everyone elses answers it is a trapped nerve resulting from an rsi. I have treated quite a few rsi cases and trapped nerves and have found that in the first instance the best approach is relaxation,heat and de stressing. Massaging the hands, arms, neck, shoulder blades and back is always an excellent place to start finishing with a face and head massage. Away from the clinic the client has to have warm baths, heat treatments and use the muscles in question as little as he/she can. Once the muscles have loosened up then it is time to work on the muscles groups affected with a little more vigour. Hands and arms should always be included in the treatment.

I had a trapped nerve once from falling over when I was Ski-ing and I had to have 2 sessions with a Chiropractioner. It did the job.

Stretching and manipulation of the muscles would help, a trapped nerve is an awfully painful thing to have, stretching is the most useful, I use stretching to relieve Carpal tunnel in my clients they find they get some relief.

This would depend on actual symptoms & site of pain. If it was radiating from the vertebrae I would refer to the pain clinic or A&E as it could be prolapsed or slipped disc . If not I would treat using deep tissue within pain threshold & specific stretches to try & release muscle trapping the nerve.