how do I keep my salad dressing from separating in the fridge?

Answer 1

You can't that's why most bottles say "Shake Well Before Using".

Answer 2

If you are making it from scratch you are not emulsifying it properly! You need to add the oil very slowly!! It is best to have room temperature ingredients also! It requires a good high speed blender,robocou, or stick blender! You cannot get a good emulsification with a hand mixer that some attempt to use!

Answer 3

If it's a simple oil and vinegar, it won't stay together for long...the two naturally don't mix.