Weeks before Wrath of the Lich King was released, with Patch 3.0, Blizzard added the Inscription profession to World of Warcraft. A scribe creates glyphs that modify the damage or effects of certain spells. At level 80 a player will have 6 glyph slots at his disposal, seperated into 3 major and 3 minor glyphs. While minor glyphs only provide a cosmetical change or remove a needed reagent cost from a spell, major glyphs are able to greatly enhance the damage of a spell or completely change its mechanic. Glyphs are created by a scribe who needs parchment and ink to create these glyphs. While parchment is bought from any trade good vendor, ink must be crafted by milling herbs into pigments and making the ink from those. Depending on the type of herb used different pigments and inks can be created. Most high end glyphs require Northrend herbs for their inks.

Just like other hybrid classes the Shaman's glyph choice greatly depends on the talent specialization of the Shaman, at least for major glyphs. Regardless of spec most Shamans will chose Water Breathing and Water Walking for their minor glyphs, as this removes the required reagent for these spells.
An Elemental Shaman needs to use the Glyph of Flame Shock, which prevents the Flame Shock DoT from being consumed by the Lava Burst crit, greatly increasing his DPS and mana efficiency. Lava Burst itself and Lightning Bolt can be improved with glyphs as well.

An Enhancement Shaman wants to improve his Storm Strike with a glyph. Depending on his choice of weapon enchants he will also glyph his Windfury Weapon and/or Lava Leash.
The Restoration Shaman has many choices and will have to decide depending on his healing style. Both the Lesser and the normal Healing Wave can be improved with a glyph. Glyph of Chain Heal makes for an interesting choice as well, as it makes Chain Heal hit a fourth target.