On EURUSD a "Pip" is th 4th decimal place of the exchange rate so = 1/100 cent, a standard "lot" is $100,000 so a movement of 1 pip is equivalent to $10. A "Pipette", is the fifth decimal place and is therefore $1 on a standard lot.
The smallest and fastest moving number on your screen is always the "Pipette" so although different instruments have different numbers of decimal places, the fastest moving will pretty much always be teh pipette, and although the standard lot "pip" is not always worth exactly $10 on other instruments, in round terms that is a pretty safe number to think in terms of.
YOU then decide what you want to risk / gain on one pip of movement and choose your own "Lot size" accordingly.
