Well now it's official, existing contracts are changed by states if they wan to. You do not believe me? Well check what Greece does to it's private debtors. So how could you expect that this won't be done by every country if the debts are too heavy? You can't, so you better do not "invest" in bonds of states. Their value is not known to you and may change if the defrauders decide that they won't serve their obligations.
The whole fiat-money systems are just playgrounds for gangster and bankster. So I would also do not invest in bank shares or bank bonds.
Anyway if you think I'm a stupid bastard, feel free to ignore my suggestions. I wish you all the luck, you'll need it.