The Punkbirder rules are pretty good ;
http://www.freewebs.com/punkbirder/selffoundrules.htm
(Excellent in fact), but there can be still be grey areas when it comes to some of the commoner and 'locally scarce' species I feel....
Anyway ... here's a couple of minor ones ...
Found 2 Red-throated Divers the other day (offshore), I find out after a look at one of the 2 main county reporting websites that 2 had been reported there 3 days before. Since they are probably the rarer of the 3 divers in the county, I feel that they were probably the same 2 birds, and probably shouldn't count them ... (But there was only 1 BT Diver reported, and I saw 3, so defo counting that one ..)
Marsh Tits ... they come to the feeders at Stithians ... I know this, so can I count them? ... (almost a moot point, as someone else called one whilst I was in the hide, so couldn't have it ... but what if I go back in a weeks time??).