1. Use the media! Media is important, use anything you have so people knows you and what you are doing. There are lots of social networks that you can use to tell the world: "hey! I'm here! i can be useful for you"
2. Before putting a price to your work, discuss with the client and see the place. This is super important. I was told something that made me think this would be a simple one-month-half-time project, so I gave a price for this. Suddenly, I realised it has consumed three months of my time, and I am doing much more work than I have thought I would.
3. Make a CONTRACT!!!! Also extremely important. Make a contract in which you specify EVERYTHING. Like what the project includes and what it DOESN'T, a description of each thing to include, delivery dates, how many chances to revise and change the project the client has (or it will become an eternal project that will have caught you like a black hole), the price, and some kind of indemnization if any of both breaks the contract. Next time, I'd rather look for a lawyer at the beginning than facing all these trouble again.
4. Put limits. If you don't put a limit to some actions, you'll discover yourself working on weekends, answering calls in the most inadequate moments, answering urgent e.mails at night, attending to last moment meetings, late and at the other end of the city, and cancelling your life not for a project, but for clients who believe they own you.
5. Keep personal life away from work. This means don't treat clients as friends . If you do so, suddenly clients will begin asking for more, and you can lose both, friends and clients. A client can be your friend, just, as said before, stablish limits and make them clear what includes your work and if you are making any kind of discount or concession because they are your friends, also make it clear.
6. RESPECT! This is so important. Don't let them shout at you, nor tell you what to do or not to. Remember, you are need nobody to treat you bad, or shout at you and there is not enough money that can pay you this. They don't own you. So no calls out of time, no shouting, no demanding, no brats trating you bad. No project is worthy enough.
7. Never give out useful information. This doesn't mean that you won't show anything to the clients until the delivery date. You can show them as much as you want, just don't give them the information. Don't give any drawing as they can end up taking it to do it with someone else wihtout paying you. Don't give them the exact model and store to buy the things you are reccomending. They could just leave you at the middle of the project and make everything themselves without paying your work. The same goes for measurements, amounts of material and so on.
9. 60-40. If the project is a one-delivery project, always charge the 60% first, and consider all the expenses when giving the budget, or you'll find yourself losing your money instead of earning some. And there is always the problem clients that won't want to pay you at the end.
10. Keep social networks away. Let's be real. Social networks are great for making people know you and what you are doing, but not for making a project. You are working in a project, in the computer or out at street, with or without internet, you are bussy. You have no time to keep checking facebook or twitter looking for the client's messages, pictures, or most recent uploaded information. That's why you have meeting. Also mails between meetings that change you everything you have agreed are not allowed, or you will never finish the project, not just not on time, but never! and you lose lots and lots of time.
11. Be true! To yourself, your principles and the project. Never do anything you don't agree with.
12. Enjoy what you do and smile! So important. The good thing about being a freelance is that you are doing whatever you like to do, and enjoy doing, that you love your work. Don't let details ruin it, just enjoy it and know when to stop not to lose your life. Remember you work to live, you don't live to work.