on the Ba.com website can you book multi stopped trips? how do you do this?
You can also book on other oneworld airline websites.
If flying to the USA for example you can book on aa.com
However if you are just starting you need to remember that you will require 2 flights on AA metal or 2 flights on a BA flight number on another oneworld member so your first run might be best booked via the phone with BA if more than one flight.
Book any internal flights within the USA on AA flight numbers as you will be classed as first for BA points purposes. Booking these on BA flight numbers will see your earning set against business. Not as good.
The BA call center will allow you to book a combination of AA and BA flight numbers on one trip.
These will often start from a European airport to reduce the cost.