general knowledge

[g.frowen]

how do i assess how much information is required before an effective decision can be made

[Numbers]

By treating each case on its merits.

[Sylday]

I doubt if there's any golden rule on this. As Lodekka says, you just have to look at each problem on its own merits, and decide intuitively how much information you need in order to reach a rational decision. But even then, your decision may be "effective", but whether it is the correct decision, only time will tell.

[Maude]

By reducing everything connected with the problem so that you can exactly express it in eight words or less. You will then clearly understand the problem, and the decision will probably have already suggested itself.