They simply ask what is your previous salary and offer a 5-25% increase. You skills are simply a pre-requisite, but they don't define your starting salary. Depending on your risk appetite and potential background checks one can lie and get a fairer deal (the firm is always protected since they have a notice period).

Three things:

1. working every hour of every day to be the best I could be and proving it on a daily basis.

2. Don't move job without taking a big raise. Play offers off against each other

3. Circulate amongst old fashioned corporates. It's easier to look good there as most of the staff are crap.