its like any field,
to succeed you need to apply yourself, make an effort and have a bit of luck.
as already stated treat your punters
look after your controller(when he or she is neck deep in account work be the first to voice in and help out)
always look after the tools of your trade(your vehicle. keep it well maintained and clean.)
and don't be afraid to admit when you don't know something or somewhere, nothing worse for a punter than a driver getting lost and the ensuing issue over the cost of the fair. happily admit your not quite sure where you are going, chances are your punter will be more than happy to oblige most times with a longer route

the above are just the obvious basics. get those right and you will do ok, give yourself a few month once you work out the busiest plots and times and what suits you best you can start getting into a groove and making as much money as you want to make. That is also the problem with this trade. I know too many drivers who complain theres no money to be made but wont start early or work late and bugger off home after 4 hours because its quiet. Personally I always start my week on a Saturday, put my outgoings (radio/car/insurance payments) away over the weekend and then leave myself the rest of the week to make "my" money theres still good money to be made in the industry with the right firm/area