I don't ride as much as I'd like, so for me its easier to mix a gallon of fuel at a time. To make my life easy (plus I'm lazy), I have a small bottle I'll pour the two stroke oil into. On the small bottle I've marked lines for one, two, and three US gallons. For the fuel I use an old empty jug that previously held window washer fluid, (one US gallon). I pour one gallon of gas into the jug, and add the appropiate oil. I run approx 50:1 (approx 2.5 oz), so my preset lines on my two stroke oil bottle and always working with one gallon of fuel at a time ensures a consistent mixture.
Just my $.02... that and $3.00 will get you a redbull..