When adding new code to an existing method, I usually datestamp it and include my initials. I ask my team members to do the same thing. This isn't a blame thing. It's all about when it got added and who added it, just in case there's a question. Sometimes I add a brief comment about why it got added. For example:
// 08/12/2016 JLC - Need to populate this other field, too, per <whoever requested it>
There are times where I don't necessarily agree with code going in, so a reason why mitigates that and reminds me later why I did that in the first place.