The easiest way to make a salad dressing is to shake the ingredients in a jam jar. Otherwise, just whisk them together with a fork. Here are some of the simplest dressings and marinades, in quantities for 1-2 people.
Classic French vinaigrette for green salads
1 tsp dijon mustard, 1 tbsp wine vinegar, 4 tbsp olive oil, salt, pepper, a pinch of sugar if you like
Italian-style dressing for salads or grilled veg
1 tbsp lemon juice, 3-4 tbsp olive oil, salt, pepper, some chopped chives or parsley and/or some chopped capers
Low-fat dressing for Asian-style salads
1 tbsp sunflower oil, 1 tbsp seasoned rice vinegar (it might sound expensive using rice vinegar but you can use less oil), 1 tsp light soy sauce
Garlic and lemon marinade for chicken
3 tbsp lemon juice, 3 tbsp olive oil, 1 crushed clove of garlic, salt, pepper and a sprig of rosemary if you have some
Tandoori marinade for chicken or lamb
1 heaped dsp (cereal spoon size) curry paste, 2-3 tbsp plain yoghurt, a little lemon and some salt