correct goal score in play trading

[bigbazzer]

ive been trying this for only a few days and started of well with profit from low scoring games such as Swindon v Charlton 2-1
Huddersfield v Millwall 0-0
Chelsea v Portsmouth 1-0
Aldershot v Rotherham 0-1
but then disaster with
Werder bremen v Bayern Munich 0-4
Ac Milan v Juventus 3-0
Oxford v York 3-1
anybody got any advice for me regards which score to trade?
oh and Dagenham & R'bridge v Morecambe 6-0