From my experience it is very hard to set rules to 'when to bluff', it is a skill that is highly situational.
A lot of it depends on the table fabric, there are tables you just cant bluff on, and there are when you can bluff often enough.
A good rule of thumb is not to bluff vs more then 2 players.
Bluffing from late position makes sense, but it is often expected and you will get called or reraised.
Another rule from bluff is to make the bluff in an amount that will actually scare people off, if you minbet vs the chip leader you will probably get called with any 2 cards.
A bluff when you can logically represent something (TP, flush,str8) is a good bluff.
A bluff has to be consistent throughout the hand, otherwise it is usually two obvious. For example if you raised heavy preflop do not try to represnet a 8,9 that completes a str8