When I first moved out of home my sister and I were living together on a VERY tight budget. We used to do stir fries, just veggies and the occasional bit of shredded pizza ham. No marinade or sauce, just straight up and dead boring.
I remember one day going to a friend's place for dinner, and he got out his wok, got out some food and started preparing a marinade. What a revelation. It had never occurred to me that you should do this (the only excuse I can make is that I was preoccupied with trying to get the marks I needed to transfer into Medicine).
I love the flavours you can impart in a marinade. The basic principle I work with is oil, sugar of some sort, acid (to break down the meat fibres and soften it) plus any other flavourings. The oil helps when cooking and the sugar just makes it nice and caramelised.
I'm doing one tonight with sunflower oil (I'm out of olive oil which would be my usual choice); soy sauce; garlic; lime and lemon zest and juice; and ginger cordial, which provides not only a nice ginger flavour but also some sugar.
Don't know what it will taste like but it smells good!