The procedure, at least to begin, is the same as a home that isn't in foreclosure. If the Seller is still owner of record, you will make an offer and come to an agreement with the Seller.
The rub comes if it's in foreclosure already, or if the price you've negotiated doesn't pay the mortgage the Seller owes. If the latter is the case, it's what's called a "short sale". If the former is the case, still not a huge deal, it's similar to the short sale in that it will require bank approval, but may also require legal work from the closing attorney.
The bottom line is, if it's in foreclosure, or the sale is going to be a short sale, it will require participation and approval from the bank. This means there are more persons from whom you have to get approval, and the process is a bit longer. It doesn't mean it can't be done, and yes, I would strongly suggest you work with an EXPERIENCED REALTOR through this process. There can be a lot of unexpected twists and turns, such as second mortgages, junior liens, unpaid assessments and or taxes in arrears, through which an experienced broker can help you navigate..
Hope this helps and feel free to contact me at firstname.lastname@example.org.
Marty Jones, CRS, CRB