A while ago I wrote a post on what galdr is, and I’ve also posted some of my own galdr, along with a photo of my own distaff. This post is on how to compose galdr using specifically the “meter of magic spells,” called galdralag. It’s entirely possible that galdr does not need to be written using this meter, but I personally find that the structure helps.
Before you can begin composing “real” galdr, you must first decide whether or not to employ galdralag and a tune in your poetry and its vocalization. Due to the uncertainty of the nature of the use of galdralag and the uncertainty as to whether melodic chanting was used at all, I cannot tell you whether you should use these things or not, as that is a decision that will vary from person to person depending on their conceptions of risk versus reward, ease of use, and aesthetics, among other things that don’t really need to be listed here. I can tell you though that you might want to compose a few practice spells, some employing galdralag and some not, and then similarly chant them using a tune sometimes, and other times not, so that you can get a feel for the meter and musicality yourself and make it easier for you to decide on your methods.