Question is a little vague…. but generally I would answer that question by saying….1) use enough emulsifier, and 2) Use a co-emulsifier.
If you are looking for a good place to start, look for an emulsifier with this INCI: Glyceryl Stearate (and) PEG 100 Stearate
It is often referred to by a designation/name that includes ‘165’. As close to bulletproof as you’ll find …. without us knowing much more about the formula.