Depends on your gunnery capabilities, plane, and your setup. If you're out front, HO into the cockpit. This works with nearly any gun package, even deer rifles. The rest of this post is assuming something with multiple cannons or many .50s. It works ok with 6x50, but works much better with 8. More guns are better guns when it comes to bomber hunting.
If you're above him and he still has at least one drone, I'm partial to coming in from straight above and raking a drone tip to tail, exiting in the direction the bomber is traveling. You have the possibility of a cockpit shot, and something will likely come off. It also gives him very little time to set up for gunnery on you. If you're off a bit, you still have a chance to hit a wingroot.
On a good gunnery day starting from straight above him, I can make my first pass, execute a barrel roll to get above him again, hit his second drone, exit to the front, and do it again, and kill the final bomber. What I have to watch out for is depending on setup and plane, the third pass I can be almost co-speed, and that puts me in gunnery range for too long. If I believe his gunnery is good or great, I will often wait after the second pass to gain some E and set up well for the third pass.
Attacking from 3 or 9 is a possibility and allows you to possibly get a twofer, but if he's not distracted, he's got an easier shot on you.
In a 262 or something with many many cannons, a 3/9 attack across the rear can net you all three planes at once just by hosing down the entire formation on the way by. However, if he isn't distracted he's got a pretty easy shot on you.
General rule of thumb, the easier a time you're having lining up your gunnery, the easier a time he is having lining you up.
Wiley.
