In many countries legal separation is a legal step married couples can take towards divorce. In many cases the couple is only considered legally separated if a court has recognized their separation. However, even with a legal separation, couples may choose to remain married.
Some countries and some states within the United States require a period of legal separation before a a couple can divorce. Laws vary from state to state and from country to country.
Separate your accounts!
There a lot of things you can do but I think the most important is to separate your accounts. Like if you have joint savings accounts or credit accounts, then get them separated so you don't have any surprises down the road!