Realty Trac posts homes that are foreclosed and homes that have had a Lis Pendens filed. If there is no sign it may be the latter. The Lis Pendens (Latin for Suit Pending) is a document filed in public records that is notification that the first step to Foreclosure has begun.
The home may not be listed for sale by any one. The seller is behind in mortgage payments. This doucment is filed and remains active even if the owner has made payment arrangements to get caught up on back payments or has filed bank ruptsy, which can delay the foreclosure for up to a year. If the seller made arrangements the Lis Pendens will remain active in public records until the end of the payment arrangement.
In answer to how to proceed. If you have an interest in the home, I would knock on the door and ask if they are interested in selling for a fair price. They can only say yes, no or maybe.
Be aware that the filing of the Lis Pendens caused a moutain of letters, cards and phone calls from investors offering to purchase the home. Many at an insultingly low price. The home owners may not be very receptive to you at first.
Best of luck