Going off this as a guide:
[i][b]the potential to do magic (which all have), the choice to use it (a spell is hardly done on accident, well a spell with the desired effect), some sort of intent (that is a desired effect), and the understanding/knowledge required to both prepare and execute the spell[/b][/i]

A glyph of power is a symbol or shape with a corporeal form which enables a user to perform a desired magical effect. Through experimenting/learning forms of glyphs, the witch gains the knowledge/understanding of the nature of the magic he wishes to perform. They are like magical instructions which determine the resultant magic executed. The act of inscribing the glyph on to objects is important, as these magical instructions are often too complex to just be remembered and spoken as words unless the magic you want is simple(VERY RARE, a picture paints a thousand words). Moreover, since the object being used to communicate these glyphs(magical instructions) is essentially a pipe/bridge/train tracks for the magic to flow, there is a need to ensure that these objects are one of value and integrity, if you desire a stronger, more lasting effect. This idea of a suitable medium ties in with the "execution" bit.

[hider=Example]
Farmer comes to Flowryde saying "Could you do me a favour? For the past few weeks a fox has been killing my chickens in the middle of the night. I've been staying up a couple of nights but that sly bastard keeps eluding me. The harvest is coming soon and I just dont have the time to build a whole new set of coops. Can you think of anything?" Flowryde thought for a bit before opening a few drawers. After a few minutes of rustling he procured a queer bundle of sticks and his carving knife. 
"This wont be permanent but it will keep the foxes away for a few weeks. All you have to do is to arrange these in an evenly spaced perimeter around the coops." The farmer appeared confused for a moment but his expression became one of confidence, as he saw Flowryde's expert hands nimbly etching intricate symbols which swirled around each stick. "These will take some time to prepare, I'll drop by your farm this evening and hand you the goods." The farmer appeared relieved. He could always rely on his friend in these matters.

The bundle of sticks was now a sack, each individually carved with the same swirling patterns. "Don't forget to activate them by touching it. Its only for single use as the wood is rather thin." Flowryde said as he dropped the sack by the fireplace. "Thanks for dinner by the way." He flashed the farmer family a warm smile before leaving. 

It was pitch black, not a tree stirred as darkness drowned the world. Suddenly, an ethereal form darted across the bushes, its bushy tail and triangular face merging with the night while he stalk his usual hunting ground. The fox was proud of himself, he had outsmarted the witch again. The smug fox approached the fence, looking for his usual burrow. Suddenly, there was a loud "BANG!" as the night exploded around him. Streams of fire erupted from the ground and sharp acrid smoke stung his eyes and nose. Pain. His senses were in agony. The sensation was unbearable. The fox regretted ever coming to farm, the chickens were too skinny anyways he thought before running away with his singed tail tucked between its legs.

Flowryde chuckled from his vantage point beside the coops. He watched as his creation did its magic. It was a simple twig soaked in brimstone and left to dry. He deviced a set of glyphs to induce heat into them when it detected an animal hungry for chickens [Stay sleeping, wake when hungry animal intends to eat chicken, when awake, heat up and show light]. The flashy display of sparks was a beautiful touch, he commended himself before resigning to the long walk back home.
[/hider]

The example shows how glyphs can be carved into sticks and such but the down side to using objects with low integrity is that they break down once the magic is used through them. [b]Runes are just small stones which are polished and can be used as a medium for glyph etching[/b]. Also note how the farmer had to activate it, for the intent and choice to use magic to play in. In this case the farmer's own magical potential was not a big factor as its just a simple heating action. 

However, the need for magical potential is pivotal is cases where highly potent glyphs are activated. For example, a Mithril suit of armour with glyphs engraved. To protect the wearer, the instructions would be: [Keep the material connected at all times,metal can not deform the armour, wood can not deform the armour, dust and grime can never dull the shine]. Instructions are explicit, and learning the right glyphs to accurately convey instructions will take a lot of studying. As a result, a magical icicle that is harder than the armour would not break the mithril armour but it can deform the mithril and still damage the wearer. Now, for magical potential, it differs from each individual. Strength of armour is directly proportional to strength of the magic user. Note, if the potential required greatly exceeds the limit of the user, the caster can die of shock, even if the mithril armour still doesnt break. The reason is uncertain. Therefore, Flowryde or glyph users who know their thang would add instructions to deactivate the instructions in the event of over exertion. 

Finally, because the glyph is a manifestation of the creator's intent, not the user's (the user merely choses to activate the glyph and wills the magic to perform). The creator's own magical potential is important for a variety of reasons. Obviously, a glyph user with low magical potential will be hard pressed discovering glyphs of power(They are not random drawings!). Furthermore, the intent of the glyph is not only physically imprinted on an object, it is also imprinted in a magical sense. Hence, glyph creator's have their unique magical signature on their creations. The stronger the magical potential of the creator, the more integrity it has. 

TL;DR: Glyphs require skill and understanding to use. Pros: Dynamic application. Cons: Limited to knowledge of glyphs, time, materials, magical potential.

The tattoo came with the character. I'm embarrassed to admit it... but I thought it looked cool so I wanted it to do something... Enhancing reflexes seemed to be the most subtle option. If you dont like it, what do you think about speed enhancement. When activated, he can run as fast as Usain Bolt. It does not shorten his life but burns up the butt fat. :brow

Did I address every issue?

Edit: Just wondering, do all of you live in America? Everyone seems to be sleeping whenever I come on :l