Wash the greens and dry thoroughly.
Strip the greens from their stems and tear into large bite-size pieces. If the stems are tender (yes for beets, chard, dandelion, mustard, etc. / no for kale and collards), chop them into 1-inch segments.
Start with a skillet that is wide enough to embarrass you at the thought of using it to cook lunch for one.
Heat it on the stovetop over medium-high heat.
Chop the bacon into 1-inch pieces and add to the heated skillet.
Cook, stirring occasionally, until the bacon is just shy of as crisp as you would like it and has given off plenty of fat. If there is more than about two tablespoons of fat in the pan, remove the rest.
If you will be cooking your stems, add them to the skillet now, along with the garlic. If not, just add the garlic. Cook, stirring occasionally, for two minutes.
Add the greens to the skillet and stir (preferably with tongs) to coat all the greens with a bit of bacon fat.
Cook uncovered for a few minutes, then add the broth, salt, and pepper.
Cover, lower the heat to maintain a simmer, and cook to desired tenderness, 5-15 minutes depending on which greens you've used.
Stir in the vinegar and cook, stirring, one minute more.
Transfer greens to a serving bowl and crumble the feta cheese overtop.
Give it a gentle stir to distribute if you like, and serve.