I was looking at my early "charts" earlier today before I knew what was up and I tested way early. Now, never before DPO 11 or 12 and only if temps are up. That being said, I've gotten all BFNs so you have to take my advice with a grain of salt!
I test whenever nobody is here to slap my hand and tell me not to. I have a 10 day LP usually, and the damn box says "test 5 days before period is due", so apparently I have tested at 5 DPO. At the time I didn't know... wasn't charting yet. But, ya. That's my shameful story.
I'm testing for the first time tomorrow, DPO16 - I know a test probably would have been accurate before now, but I have a longer cycle so I wanted to wait until a bit later on.
Re: when do you normally test
The earliest (and only) time I've tested was 10 DPO on New Years Day. I'm holding out for 14 DPO, if it comes.
I think they recommend at least 1 day after missed period for the best accuracy.
BFP #3 -mm/c @ 7wks, discovered at 9wks, D&C 9/28
BFP #4 5/29 EDD 2/9 - please be our rainbow