... some of the arms-granting groups have people who can help walk you through the process. (Make sure it's an official organization, not the fly-by-night type that try to sell everybody the same symbol!) Plus the person should know about your national heraldic tradition and the types of rules which apply ... you can do things in Scotland which probably wouldn't be apt in Poland, in terms of the choice of devices, even though the general heraldic rules about which colors can or can't be juxtaposed may be similar.
This SCA explanation gives a (rather funny) example of what it's like to get an application through the system. Not being a centuries-old organization, their system is probably much simpler and more streamlined than for one of the real places ... many years ago, I did some volunteer work for the Heraldry Society of Canada. It took months to get some of the badges cleared (in terms of checking for similar symbols, and making sure that the ones submitted weren't too bizarre or inadvertently rude). In one case, something made it as far as the drawing board before we had to abandon it because it was based on an incorrect translation from the French ("rudder" not "paddle").
http://www.pbm.com/~lindahl/cariadoc/heraldic_devices.html"The organization in the SCA that registers heraldic devices is the College of Heralds, represented in each barony or shire by the local herald. The procedure works thus: you go to your local herald with a design, for example a pink biplane on a blue background. He explains that (1) pink is not a heraldic tincture, and (2) biplanes are not really suitable on a device to be used in a medieval organization. So you redesign with the herald's help and come up with something which as far as he knows satisfies the rules of heraldry and is not too similar to existing devices. You then fill out quite a lot of forms, and your herald sends them off to his superior at the kingdom level. Three months later she sends you a letter explaining that the device you submitted is almost the same as the arms of the Whosit family of Scotland. You redesign so that your proposed device is sufficiently different from the Whosit arms and send it off again. If the kingdom herald approves your device it is sent on to the chief herald for the Society; if he approves it, it is registered as yours. From then on, no one else in the SCA may use it, and no one may register something very similar to it without your express permission."
http://www.pbm.com/~lindahl/cariadoc/heraldic_devices.html