The spec is fun in non-rated BG because organization level often is at 0 and you meet a lot of bad players there, and thus you can exploit this pretty well with Destruction compared to the other specs in terms of fun. You can control your target(s) pretty well with destruction too if you know how to play it.
In arena it's much harder. People can still be bad there, but they're always organized (relatively at least), and they will tunnel vision you when they realize you're a destruction warlock and the healer will mostly likely tunnel the dispel button, effectively reducing your presence to nothingness.
A destruction is extremely hard to play properly, but has OK synergy with a fire mage and possibly a rogue. However, the class you're playing with is only 30% of the fight, the real challenge is proper team work.
For the Prime Glyphs, I use Conflagrate, Chaos Bolt and Immolate. Conflagrate is your highest damage source, and you want this available at most time. Immolate is the source to a lot of your damage, and it also increases damage of Conflagrate. Chaos Bolt is weak for what it is, but it nevertheless has relative short cast time, and what I value most with this glyph is more Soul Leech procs.
For the Major Glyphs I use Soul Link, Shadowflame and Seduction. I realize this area is more controversial, so I won't go into details. Basically do what suits you best. Glyph of Demonic Teleport is also very useful.
As for reforge. I first of all make sure I have 4% hit (no more, no less), this is incredible important. Then I reforge everything else into haste until I get 10% without Dark Intent. At 10% you gain an additional tick to your Immolate (8.3% for corruption IIRC). This is very important, as it greatly improves the damage of Conflagrate as well. If Dark Intent is dispelled, which is very likely in many circumstances, you still have that extra tick.
After 4% hit and 10% haste, I reforge all mastery and any exceeding hit and haste to crit. You should however go for what suits you best; this is also a controversial area. I don't like mastery because it basically serves as a weak version of the intellect stat, and it doesn't increase damage of several of your used abilities, such as Bane of Doom, Corruption, Shadowfury and Shadowburn.
Hope that helps a bit.