I guess the obvious thing to do is to send samples of your work (appropriate to the publication) to magazines etc and websites, and then phone up a couple of weeks later to check it arrived. THEN have it handy to fax when they claim they never received it! Also have you got a good accountant? You will need one if freelance, and also you will need to keep ALL receipts of anything you buy (and more) that is linked with your work. An accountant will be able to tell you how to do this in your favour, including things like "working from home" costs and travel to anywhere outside your work (home).