Steps I take before merging:
1) Confirm that the basic biographical information is similar.
2) Check the biography, see if there is additional information that is needed to confirm or deny the merge.
3) Search name and birth date to check for duplicates (we want to merge into the lowest profile, which may or may not be the one proposed). If the proposed merge is not into the lowest, 3rd profile, I remove the merge and merge both into the final profile.
4) Merge profiles, keeping track of differences (aka, "Birth date could either be 1850 or 1847") and add them back to the profile.
5) go through the profile, clean up the biography, and do any further pending merges or proposals (spouses, children, etc).