CrazyKinux, owner of the Eve blogpack, has just posted an excellent guide on how to start an Eve blog. Much of his wisdom is good for general consumption. So if you want to start a blog about MMOs in general or the game of your choice then go ahead.
One bitter lesson I'll pass on though. If you start a blog about a game make sure you are mainly playing that game. I started blogging about Holy Paladins. Then I stopped playing my Holy Paladin and started playing a Death Knight. So I made a new blog about Death Knights. Then I stopped playing WoW and started playing Eve. So I started a new blog about Eve. Then I realised that was a silly way to proceed and started a new blog about MMOs in general. Even there I occasionally veer off-topic.
Best of luck to any new bloggers!