The Tengwar was originally developed by the Noldor, a kindred of the Eldar, and went through several versions before it was introduced by the exiled Noldor to the Edain and Númenoreans as The Tengwar of Fëanor and thus became known as The Fëanorian Letters.
The Tengwar were the letters which the Elves, and some Human scribes, used. Each region or culture had different "modes" of writing, assigning some slightly different values to the letters. It is entirely possible, and fun, to use the Tengwar to write English.
In game, the devs have shown a fondness for converting English to a phonetic spelling, then scribing the phonemes in Tengwar (or sometimes the dwarvish runes called the Angerthas). This is commonly seen in the glowing runes scribed in the air by various magic-using classes in the game.
The Quenya language had some unusual phonemes and totally lacked others common to Sindarin. Where Tolkien notated such differences we display it as (Q: ).
|IV||8||ungwe||g(gw) (Q:ngw)||spider's web|
|III||11||aha (harma)||sh(hk)||rage (treasure)|
|III||19||noldo||"one of the kindred of the Noldor"|
|6||I||21||óre||untrilled r||heart (inner mind)|
|II||22||vala||w (Q:v)||angelic power|
|30||silma nuquerna||s||opposite of starlight|
|32||áre nuquerna||z||opposite of sunlight|
|blank space used to separate words|
|one sign used to end a sentence|
|one sign used to end a paragraph or document|
About Vowels - In Quenya vowels were drawn above the consonant they follow (as Quenya had very few words that started with a vowel). Sindarin was the opposite, but both allowed the use of a tehta (sign) which J.R.R.T. referred to as a short carrier. The most commonly-drawn form of this short carrier looked like an un-dotted i (short vowels) or j (long vowels) and the vowel could be placed over it. The scribes of Gondor used this tehta almost exclusively, very rarely placing vowels above consonants. All three practices are valid and, because it is easier to do in wiki-code, we choose to follow the scribes of Gondor here.
Disclaimer: The Etymology of language, and its use, was Tolkien's field of expertise and his appendices describing the languages of Middle-earth were written by a scholar to other scholars. As such, unless we also happen to be an Etymologist, we can barely hope to fully understand his meaning. We are doing the best we can.