I’ve read The Hobbit, the Lord of the Rings trilogy, and The Silmarillion[sic?]. Since Tolkien did such a good job at outlining his beautiful world, I have a plan to not only reread those, but to expand my knowledge to perhaps rival even that of Qadgop.
Where should I start?
Read them again.
And yet again.
Read all written by The Master himslf, then read the Cliff notes (No kidding, they do tell alot)
Read what also may be written about what JRR wrote.
You’ve got alot of work if you’re willling to try to catch up with the Q Man. Better brush of on your Sindarian(sp?)!
Happy Reading.
You should actually stop now unless you’re really really fascinated by the prospect of knowing that the name of Mim’s slain on Khim was actually Qim until the 5th draft of the story happened and Tolkien spilled some tea on the page and it smudged the name thus changing it thereafter (or some equally mind numbingly meaningless detail).
I love Tolkien…I love him to bits. But I Hate the idea that people are compelled to pick his mythology to bits by poring over every last scrap of his ‘notes’ trying to understand his glory. He was an obsessively geeky professorial type who wrote some brilliant tales…let’s just leave it at that. Once you are past Unfinished Tales you’re pretty much into the land of Chris Tolkien’s obsession (and happily for him ‘career’) and your own slide into hopeless nerd-dom.
Check out this thread. Then start reading HOMES.
http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=228561
Get “The Atlas of Middle Earth”. Read the Sil & UT with it on your lap. Take notes.
Start making up limericks in Quenya. Give endearing names to household objects and pets in Khuzdul (dwarvish). Curse at your children in the Black Speech.
Visit the Marquette University Library’s JRRT manuscript and drawings display.
Inform a loved one that in his notes JRRT actually gave Lobelia Sackville- Baggins 3 different but related first names in the “common speech” based on a flower, yet never even used any of those 3 names in LOTR or any writing published in his lifetime. Get a blank stare back from said loved one.
Then get back to me.
Sindarin
In all seriousness, after you’ve read The Silmarillion a time or two, pick up Unfinished Tales. Most of the material in there is far better than that in the published Silmarillion (and that’s saying a lot), except for the fact that it’s unfinished. But I won’t actually recommend The Books of Lost Tales, unless you’re interested in the process of writing, rather than the end result.
Get a girlfried or boyfriend as your tastes dictate. That should kill this desire.
I keed! I keed!
::D&R::
You are a god to me. 
Bwa ha ha!
For advanced students: Worry about getting Fingolfin’s and Finarfin’s lines confused. Devise a mnemonic for avoiding mixing up Fingon and Finrod. Lull yourself to sleep at night by tracing Noldor genealogies. Know Fingolfin’s wife’s name. Be able to recall all 7 of Fëanor’s sons’ names. Extra points: Name which son you think was the biggest dick. Explain why.
Also: Feel bad that Bor’s descendants probably got abuse for Ulfang’s bad deeds. Wonder if Ælfwine had a chemical dependency problem.
The place to start? Why the
Custom Tolkien Booklist of course. Written by one of the most knowledgable of Tolkienphiles it is a script which rates which books you would be most interested in. While you are there also read the rec.arts.books.tolkien FAQ. This is a great primer on the most discussed topics on the Tolkien forums. It also will show which books yo might find more interesting. They tend to be quoted more often.
As for reading preference. In general my recomended reading order would be:
1- The Hobbit
2- The Lord of the Rings
3- Unfinished Tales
4- The Silmarillion
5- The Letters of J.R.R. Tolkien (ed. Humphrey Carpenter)
6- Morgoth’s Ring and The War of the Jewels (HoME X-XI)
7- The Peoples of Middle-earth (HoME XII)
8- The rest of HoME (HoME I-IX)
9- Tolkien: The Authorized Biography (by Humphrey Carpenter)
10- Pictures by J.R.R. Tolkien
11- J.R.R. Tolkien: Artist and Illustrator (eds. Wayne G. Hammond and Christina Scull)