I have seen many different ways that people use to decide what glyphs to craft. I plan to talk about the details of all the ones I can think of in later posts. I am going to start with the one I use and the one that is related the mod I wrote. I am posting about this before I talk about the mod so you understand the power of the mod a little better.
The full stack method is fairly simple. You don't have to make full stacks, any set number will work and it will depend on your market. I use a stack of 14. Some do 2-3 and others will do the full 20. The idea is you make a full stack and the next time you craft you fill that stack back up.
This way you are restocking inventory. It is very easy to see how many of an item you have and knowing how many you need to restock with. Altaholic is the mod I use to see item count. It is great to use even if you don't have any alts. After you crafted that next batch, every time you restock, you are making a glyph that sold. It is the backwards way to track sales but it works.
When you sit down to do your crafting, anything that has a full stack in your inventory is something that does not sell well. The number you craft shows you how well it did. All the single and double glyphs that you craft show you how many you sell by having a wide spread. Those are the strange spec or worthless glyphs that nobody buys very often. The more different glyphs you post then the more of these sells you will get.
The glyphs that you have to craft several of are your popular ones. If you ever have to craft a full stack, you know that you ran out of that item. This would be a good item to craft extras for. The more glyphs I craft, the more extra glyphs I craft. I bet I make 20% more of the item I sell out of. Let the stack size tell you whats going on.
If I craft every single glyph in my craft list. I can mindlessly just check the count on each one. Some glyphs sell for nothing and other for a bit more. There are also those few glyphs that you never know what price it will go for today. Those are the glyphs that get misses when you only craft the good sellers. When a glyph like that hits a dry spell, it falls out of sight and you are not there to get sales when it recovers. If you use the stack sizes, you are ready for any glyph to bounce back.
This system is very mindless. I don't care what sells or for how much. I don't care how often something sells. I don't care what the popular thing to do is. I don't care whats a raid or pvp glyph. I don't care if its a good or bad one. All I care about is getting my stack full every time I craft.
Pro Tip: Instead of crafting the glyphs that sell for nothing, buy them off the AH if you can get them for less then the cost of mats.