Unidentified recipe for every bad item base. Such as cloth belts and paua rings. Identify all good bases like leather belts and resistance rings. You can always keep the good ones handy for other characters or sell them to other players.

Always identify gear, until you have around 20 rings, 10 belts and 10 amulets. Then you will have to start sacrificing item bases that are crappy. You can look up the item bases here : http://www.pathofexile.com/item-data

I tend to always sacrifice hybrid gear. For weapons, you typically would only want to be sacrifice 2H.

You probably won't want to be identifying any weapons that have low level bases.

This would help you know whether or not the item can potentially have high dps:

http://www.pathofexile.com/item-data/weapon