With the complexity of shield mitigation there isn't an easy way to work out the optimal targeting for a battle between two fleets of cap + frigs.

Personally I tend to use my cap to drain their cap shields, and my frigs whittle down their forces with focus fire until I clearly have strength of numbers, then switch to focus on the cap once the shields are down. It always seems that if I focus solely on the frigs first my cap suffers heavily.

Just curious to what others have found (even though release will likely be different).