First of all go job hunting , dont wait for people to come at you. Browse forums with artistic job offers , promote yourself etc. In time people wll come at you but internet is a shouting contest , if you dont shout out loud your invisible.
Always get paid before you draw unless you are CERTAIN about your client' decency. You are in the risk , not the client. If you decide to be a funnyman and walk away with the money , you are fucked. The client will make sure everyone knows your a thief and just a hint of rumour about you being a thief can decapitate your career. Whose gonna trust you? On the other hand , if the client is a thief , you can do nothing about it. You will waste time and effort working on a piece that you will never be rewarded for. Time and effort= $ , always remember that.
Keep a balanced gallery , dont flood it with your commissioned work only. Make sure you have personal pieces in your portfolio , these are the ones that will attract clients , not the portrait of some guy's grandma.
Be friendly , be humble , dont be an asshole. Before anything we are humans. When someone trusts you with his money and his ideas , he expects that you are at least kind to him. There are tons of other artists and many are better than you , no matter how far you have progressed. The fact that he chooses you is important. Make sure that your attitude will reward his choice. Then , he will come back to you and if someone asks him , he will say "go to this guy , he is a good artist AND a good person" Its not rare for employers to ask past clients of yours their opinion about you. This is not bullshit , its fundamental in marketing. However..
Dont be afraid to say no. Sometimes people ask ridiculous things for ridiculous payment. Sometimes you are too flooded with work that if you take up more , you will just dissapoint clients. And sometimes , you just dont feel like working on the topic you are asked to do. You are not a slave. Dont be arrogant but also , know your worth and demand that the people you are working with aknowledge it aswell.
And get ready for some bitter moments. Life has its ups and downs. They will turn you down , ignore you , sometimes steal you , its all part of the business. Learn how to handle it and move on , keep getting better.
Hope i helped :)