First, squeeze the juice of 1/2 Lime into a small bowl (lemon is okay if you don't have limes)
Next crush a couple of cloves of Garlic with a garlic press into the Lime juice.
Then add a teaspoon of Olive oil, and half a teaspoon of Mustard. The Mustard acts as an emulsifier and keeps the Olive oil and Lime juice from separating. (I use brown mustard, but any kind is okay)
Last, add herbs and spices: Black Pepper, Red Pepper Flakes, Rosemary, Mint, Basil, Oregano etc.
I don't usually put in all of those spices: I leave out the Red Pepper if there are kids or spice intolerant adults. I normally use Mint or Rosemary, but not usually both etc. And, I like to add salt while grilling rather than in the marinade. When we have fresh Rosemary or Mint, I like to chop it up finely before putting it into the marinade.
The marinade should be pretty thick, I normally spoon it onto the Lamb Chops and then spread it around. You can put the marinade on the meat a day ahead of grilling, but most of the time it is applied no more than 30 minutes prior to grilling.
Added Note: I use almost exactly the same mixture for grilling Salmon (fillets or steaks), just leave out the Mint and Rosemary. You have to grill the fish the same way (not as long though) as the lamb--directly on the grill, over the coals. No wrapping in foil.