For outdoor fill flash, spot or evaluative metering ?

What is the preferred metering method when shooting outdoors in sunlight and using a flash for fill, camera in AV mode ?

Spot or evaluative ?

Would it change depending on where the sun is (behind or in front or sides, etc) ?

Each metering mode has its place. Whether or not you're using fill flash really isn't part of the decision-making process. I would encourage you to read the camera's instruction manual thoroughly and practice with all metering modes (Center weighted average, evaluative, partial, spot) to get a feel for how they behave.

Keep in mind that the camera's metering mode won't affect the flash exposure. E-TTL flash uses a totally separate metering system. Default is Evaluative, and in the camera's menu system you can switch that to Average. Using the Flash Exposure Lock button is like spot metering for the flash exposure.

Thanks Curtis, I actually dug up my Speedliter's Handbook and started reading up on the different modes....time to practice !