I use this simple one all the time. Mix some Grey Poupon mustard with some balsamic vinegar. I throw some boneless skinless breasts in a bag with this mix about an hour or so before I throw it on the grill and it comes out great.
It’s very mild but not boring so you can throw the chicken on anything.[/quote]
I do the same basic thing except I add olive oil to the mix. It turns it into a mustard vinagrette so I can make a huge batch and use it with fish, chicken or salads.
A marinade consists of some basic stuff. First, an oil. Second, an acid (vinegar or citrus juice works perfectly). Finally, you only need to add some seasonings.
I have found that 1/2 cup of oil and 1/4 cup of acid works perfectly for 8-10 chicken breasts. The seasonings depend on how salty, peppery or whatever you prefer. Play around with this and you can come up with your own favorites.