One of the things that always sends me searching through my old code is rounding. I can never remember the syntax and the Apex documentation on Decimal methods on the Salesforce Developer site doesn't provide any examples inthe description (Its somewhat hidden up in the Divide method description if you look for it) . So, I thought I'd put a few examples here as a reminder to myself and to share with everyone else Googling it. 

Decimal numberToRound = 12.345;
Decimal roundedUp = numberToRound.round(roundingMode.UP); //result: 13
Decimal roundedDown = numberToRound.round(roundingMode.DOWN); //result: 12
Decimal scaled = numberToRound.setscale(0); //result: 12 – no rounding specified, just removes decimal places
Decimal scaledUp = numberToRound.setscale(0, roundingMode.UP); //result: 13 – no rounding, just removes decimal places

Look at the documentation on the RoundingModes for more detail on Ceiling, Half_Down, Half_Up, etc.