That depends on the relationship.
If you can, keep it friendly. Talk out how you want everything split, and share an attorney who will draw up and file all the appropriate papers.
If you can't keep it friendly ... And there are kids ... Keep the best interests of the kids in mind.
If you can't keep it friendly ... And there are NO kids ... Protect your interests by getting the best lawyer you can. Ask around. Remember that some people will bad-mouth a lawyer who "took them to the cleaners" - and you may want THAT lawyer.