If you've just got the xbox, watch out for the online deals - don't go paying £39.99 for 12 months.........
Ours was registered last month, so 'Gold' runs out on Xmas day........... didn't press buy, or purchased a card (the cards can be got from amazon for about £30) and got offered a 1 month Gold for £1 and 2 free games............. Once renewed, I've been offered monthly renewal for £2.50 - so can do this shortly, and only pay MS £30 per year............ (to run from late Jan) not £40 - so still get the discount.............
So don't go mad renewing, and wait for an offer via your login page, otherwise buy a prepay card.
Got about 10 games now, and aiting for Sonic racing game - that should be fun online (PS my kids are 10 and under so Halo Reach is mine only)