If you play GWX, look into the manual for a list of historical operations that have been scripted in. Then it's only a matter of being in the right place at the right time. Sometimes the game will also spawn capital ships in the middle of convoys, but to my knowledge it's totally random and there isn't anything you can do to encourage that (so hunt convoys and keep your fingers crossed...). And if it's still early in the war you can raid ports. Scapa and Gibraltar pretty much always have juicy targets. Keep an eye out for mines, subnets, and plan your escape carefully though. Last but not least you can also try to go after task forces. They're generally faster than your boat at flank so take care to position yourself right into their path or you'll miss your chance... And as I've just learned, not all task forces are created equal; you might find torpedo boats instead of capital ships
