the best thing about trophies/achievements is that your motivated to play a game on harder difficulty levels.

when i was young i just played games on easy to complete them and i couldnt be bothered to play them again.

now thanks to trophies, i tend to playthrough on normal and then on hardest difficulty. in some games like deadspace and resistance 2 where you unlock the hardest mode after playing on the previous hardest mode, ive ended up playing through 3 times.

usually on normal, but if there's a trophy/achievement involved I might up the difficulty.

Almost always the hardest.

But since zexen is a meanie, he made me start Persona 3 on Medium!

what ever the hardes setting is.

depends on the type of game, But normally normal the first time through and then again on hardest setting.

I let the game decide.

I enjoy playing and experiencing the game as the developers intended me to.

i  normal paly the medium diffucilty so i can enjoy the game the first time then after if i liked it i would go and play on a harder diffucilty.

If I buy a new game that I haven't got used to playing yet then I would just start on normal. But when I learn to play the game I would go for the next available difficulty.

Mostly medium but there are some puzzle games I play in hard (after I played the Easy and Medium difficulties)

I always start on the Normal/Medium Difficulty and I hardly attempted the harder/expert difficulties until this gen when trying to get Platnium for Uncharted 2 and GOW III, etc.