I usually just use plugs if I'm shooting outdoors. Used to use disposable foam ones a lot, because I had a huge box of them that never seemed to run out. I'll agree, putting them in correctly is very important to how well they stay in, as well as how well they actually work. You really have to smoosh them down well and evenly before you put them in your ear. I always keep a few just about everywhere. Range bag, glove box etc...
I have a pair of the Surefire Defenders, I'm not sure where I bought them, but I think it might have been Security Equipment. However, I notice that they start to hurt after 3 or 4 hours of wearing them straight. I may just have slightly a wrong size, I know they come in small, medium and large. The thing is, I always have a tendency to misplace them. I'll put them in a pocket, and dump them somewhere random when I empty my pockets at home. Or I'll toss them in my range bag, or one of my cases, and forget which pocket it's in.
Most days I use the Mil Spec Monkey "cool guy" hat that I bought from Dave at Mojo. It comes with a pair of retractable, rubber baffled ear plugs. They work well enough for outdoor shooting, and it is very hard for me to misplace a hat. But as with all rubber baffled ear plugs, they take a bit of playing around with to get a proper "seal" in your ear. Some fiddling, some tapping, and a snapping your fingers right next to them to see if they are seated properly.
The only time I wear muff, is when I'm shooting indoors. At which point I'm usually doubled up with foam plugs and a basic pair of muffs.