Glyphs draw on energies by connecting representations of various power wells, the positions of which in the sigil must be at precise proportionate distances from each other to work. The overall orientation is irrelevant.
There are eight known wells (with rumours of others - no longer working ones - used in older glyphs) : four control points which are believed to be required by every glyph, and four effect points which give distinct energies that define the power provided. Usually only one or two effect points are used in a glyph.
Exactly how each point manifests in a glyph is defined by the angle at which the line (usually a straight line) passes through the point in relation to the other points. Only a fraction of the line to either side of the point affects the glyph, with most of the connective lines being left to artistic decisions - which can identify a particular glyphmason.
The fixed points control the Duration, Power, Range, and Trigger.
The source points are Decay, Life, Pull, and Strength.
Multiple effect points can be used in a glyph either to produce multiple effects, or to combine them. In the former case the connective lines should pass through fixed points; in the latter a line must connect the effect points without passing through a fixed point. These obviously add a degree of complexity to the glyph, but a combined effect is more common because it has a single effect, and multiple effects often need to be triggered in a particular way in order to avoid using up too much energy.
Any inscribed glyph can work, so most people know not to randomly write them down, or randomly doodle anything which could happen to duplicate a glyph. Even a glyphscribe won't write the whole thing out as one before the actual inscribing. All glyphs are recorded as halves. While a horizontal split is safest, a diagonal split tends to be more common among the uneducated, although it rarely causes a problem (a diagonal leaves the power and trigger in the same section, so should the lines be accidentally linked it could have unforeseen effects).
While glyphs may be carved directly into materials, the power they use can often weaken and break the material unless it has been specially prepared. This weakening means the area around the lines is likely to crumble away, which in turn weakens the glyph until it stops working. Using certain materials to draw the glyph on a surface enables it to last longer before the surface inscribed on begins to wear away. Using materials within carved glyphs produces the most durable ones - especially if using arvinim - but these also tend to be the most expensive.
When glyphing buildings or suchlike to increase their durability, it's usually achieved by using a reasonable inscribing material within the carved low power glyph. Done correctly, the strengthening makes the structure's material more resistant to breaking from the glyph, so even once the initial inscribed material burns out an equilibrium is reached that keeps the carved glyph from breaking down for longer than natural wear would take.
Some glyphs on buildings may be triggered, such as fireproofing wooden structures. The glyph is triggered by the flames, and while it's likely to be damaged by the glyphs power - and will probably need replacing - it will prevent the spread of the flames.